2x^2-4x+8 when factored is

Answers

Answer 1

Answer:

[tex]2(x^{2} -2x+4)[/tex]

Step-by-step explanation:

[tex]2x^{2} -4x+8[/tex]

= [tex]2x^{2} -2*2x+2*4[/tex]

= [tex]2(x^{2} -2x+4)[/tex]


Related Questions

The scores of James in his math test are 75, 78, 89, and 71. What score on the next test will make James’ average at least 80 ?
x > 87
x > 87
x < 87
x < 87

Answers

Answer: x ≥ 87

Step-by-step explanation:

Set the minimum score on the next test as x & calculate it:

[tex]\frac{75+78+89+71+x}{5} =80\\\\75+78+89+71+x=80(5)\\\\313+x=400\\\\x=400-313=87[/tex]

So they need at least a score of 87 for the average to be 80+.

Answer:

x ≥ 87

Step-by-step explanation:

What is the value of the expression: 4+42 +22

Answers

Answer:

84

Step-by-step explanation:

[tex]4^3+4^2+2^2= 64+16+4=84[/tex]

[tex]\huge\text{Hey there!}[/tex]

[tex]\huge\boxed{\mathsf{4^3 + 4^2 + 2^2}}[/tex]

[tex]\huge\boxed{\mathsf{4^3}}[/tex]

[tex]\huge\boxed{\mathsf{= 4 \times 4 \times 4}}[/tex]

[tex]\huge\boxed{\mathsf{= 16\times 4}}[/tex]

[tex]\huge\boxed{\mathsf{= \bf 64}}[/tex]

[tex]\huge\boxed{\mathsf{4^2}}[/tex]

[tex]\huge\boxed{\mathsf{= 4 \times 4}}[/tex]

[tex]\huge\boxed{\mathsf{= \bf 16}}[/tex]

[tex]\huge\boxed{\mathsf{2^2}}[/tex]

[tex]\huge\boxed{\mathsf{= 2 \times 2}}}[/tex]

[tex]\huge\boxed{\mathsf{= \bf 4}}[/tex]

[tex]\huge\boxed{\mathsf{= 64 + 16 + 4}}[/tex]

[tex]\huge\boxed{\mathsf{= 80 + 4}}[/tex]

[tex]\huge\boxed{\mathsf{= \bf 84}}[/tex]

[tex]\huge\boxed{\mathsf{Answer: 84}}\huge\checkmark[/tex]

[tex]\huge\textsf{Good luck on your assignment \& enjoy your day!}[/tex]

~[tex]\huge\boxed{\frak{Amphitrite1040:)}}[/tex]

Peter plays basketball. In one game, he needs to score at least 38 points to have a
season high of 1,200 points. He scores x number of 2 pointers and y number of 3
pointers and meets his goal of at least 38 points.
Using the variables given, write an inequality describing this scenario.

Answers

2x + 3y > 38

I am currently on mobile, but the > should have a solid line beneath. I know that 2x + 3y needs to be greater than or equal to 38, since if he scores less than 38 points he won’t meet his season high of 1,200.

Y and x have a proportional relationship, and y=4 when x=12

Answers

Answer:

multiply 4 by 12 okay bro

Answer:

y = [tex]\frac{1}{3}[/tex] x

Step-by-step explanation:

Given that y and x are proportional then the equation relating them is

y = kx ← k is the constant of proportion

To find k use the condition y = 4 when x = 12 , then

4 = 12k ( divide both sides by 12 )

k = [tex]\frac{4}{12}[/tex] = [tex]\frac{1}{3}[/tex]

y = [tex]\frac{1}{3}[/tex] x ← equation of proportion

Help please and thank you

Answers

Answer:

x = y² - 7

Step-by-step explanation:

the inverse function is simply an exchange of x and y (and then the simplification happens to transform the whole expression back into a form y = ....)

If the area of a rectangular field is x2 – 3x + 4 units and the width is 2x – 3, then find the length of the rectangular field.

Answers

Answer:x²-3 x+4/ 2x-3 units

Step-by-step explanation:

Area = Length * Width sq. units

x^2 - 3x + 4 = Length * 2x - 3

=>Length = x^2- 3 x + 4/ 2 x − 3 units

HELP ME WITH THIS PLS IM FAILING REALLY BAD ITS PYTHAGOREAN THEOREM

Answers

Answer:

50 km

Step-by-step explanation:

c = √a^2+b^2

=√30^2+40^2

= √900 + 1600

=√2500

= 50 km

Answer:

50km

Step-by-step explanation:

The price of 5 kg of rice is ₹83.75. How many kilograms of rice can you buy for ₹670?

Answers

Answer:

40 kg

Step-by-step explanation:

[tex]\frac{5}{83.75} :\frac{y}{670}[/tex]

y · 83.75 = 5 · 670

83.75y = 3350

83.75y ÷ 83.75 = 3350 ÷ 83.75

y = 40

The amount of rice you can buy for ₹670 is given by the equation

A = 40 kilograms

What is an Equation?

Equations are mathematical statements with two algebraic expressions flanking the equals (=) sign on either side.

It demonstrates the equality of the relationship between the expressions printed on the left and right sides.

Coefficients, variables, operators, constants, terms, expressions, and the equal to sign are some of the components of an equation. The "=" sign and terms on both sides must always be present when writing an equation.

Given data ,

Let the amount of rice for ₹670 be A

Now , the equation will be

The amount for 5 kg of rice = ₹ 83.75

So , the amount for 1 kg of rice = amount for 5 kg of rice / 5

The amount for 1 kg of rice = 83.75 / 5

The amount for 1 kg of rice = ₹ 16.75

So , the amount of rice for ₹ 670 = 670 / amount for 1 kg of rice

The amount of rice for ₹ 670 = 670 / 16.75

The amount of rice for ₹ 670 = 40 kilograms

Therefore , the value of A is 40 kilograms

Hence , the amount of rice is 40 kg

To learn more about equations click :

https://brainly.com/question/19297665

#SPJ2

what is the equation in slope intercept form 3 y - 9= 12x please help fast ​

Answers

Answer:

Step-by-step explanation:

Slope intercept form is y = mx + b where m is the slope and b is the y intercept SO

y = mx + b

3y - 9 = 12x

3y = 12x + 9 (divide by common denominator 3)

y = 4x + 3

(4 - 5)^2 + ( 2 + 1)^2
——————————
( 4 + 2)^2

Simplify using the order of operation

Answers

Answer:

[tex] \frac{5}{18} = 0.27[/tex]

Step-by-step explanation:

[tex] \frac{(4 - 5)^{2} + {(2 + 1)}^{2} }{ {(4 + 2)}^{2} } [/tex]

[tex] = \frac{ {( - 1)}^{2} + {3}^{2} }{ {6}^{2} } [/tex]

[tex] = \frac{1 + 9}{36} [/tex]

[tex] = \frac{10}{36} [/tex]

[tex] = \frac{5}{18} [/tex]

= 0,27

what does the rational form of the ratio a:b look like

Answers

Answer:

a/b

Step-by-step explanation:

The rational form of a:b or simply a/b is in the simplest form.

Answer:

Step-by-step explanation:

the answer is option 2 from the above sheet

142°
3xº + 22°
X=
degrees.

Answers

Answer:

x = 40°

Step-by-step explanation:

The 2 angles are vertical angles and are congruent , then

3x + 22 = 142 ( subtract 22 from both sides )

3x = 120 ( divide both sides by 3 )

x = 40°

Answer:

10000+1241222+24122+907979+153647612232

1

The lengths of the sides of a triangle are 3, 3, 312. Can the tangle be a right triangle?

Answers

Answer:

Yes it can be right angle triangle

Olivia is fixing her bicycle. She starts fixing it at 9:34 am and finishes at 1 pm. How much
time did she spend fixing her bicycle?

Answers

Answer:

3 hours 26 minutes

Step-by-step explanation:

26 minutes(9.34am to 10am)+3 hours(10am to 1pm)=3 hours 26 minutes

The total time that she spend fixing her bicycle is 3 hr 26 minutes

Calculating total time

Given the following parameters

Time that Olivia starts fixing bicycle= 9:34 am

Time she finishes = 1pm

The total number of hours spent from 9:34am and 12:34pm is 3 hrs. The remaining minutes to 1 pm is 26 minutes.

Hence the total time that she spend fixing her bicycle is 3 hr 26 minutes

Learn more on time here: https://brainly.com/question/2854969

#SPJ6

In this activity, you will create an equation for a function represented by a verbal description.

Vicky charged her phone’s battery to 100 percent. Then she took the phone off the charger. When her phone is off the charger, it loses 5 percent of its battery life every hour. What function models the percentage of battery life left in terms of the number of hours since Vicky took it off the charger?

What is the initial value of the function? Is it positive or negative? Explain your answer.

What is the function’s rate of change? Is it positive or negative? Explain your answer.

Answers

Answer:

1) The initial value of the function is the y-value when the x-value is zero. The number of hours is the x-value and the percentage of battery life left is the y-value. When the number of hours, x, is 0, the percentage of remaining battery life, y, is 100 percent. So, the initial value of the function is 100. The initial value is positive because the percentage of remaining battery life cannot be negative.

2) The rate of change is the rate at which the y-value changes with respect to a change in the x-value. When off the charger, the phone loses its battery life at a constant rate of 5 percent per hour. So, the function’s rate of change is -5. The rate of change is negative because the rate indicates that the percentage of remaining battery life decreases as the number of hours increases.

Step-by-step explanation: I just did the tutorial right now i hope this helps

Answer:

part a = The number of hours since Vicky took the phone off the charger is the independent quantity, so the variable x should represent it.

part b = The percentage of battery life left in hours is the dependent quantity, so the variable y should represent it.

part c = The initial value of the function is the y-value when the x-value is zero. The number of hours is the x-value and the percentage of battery life left is the y-value. When the number of hours, x, is 0, the percentage of remaining battery life, y, is 100 percent. So, the initial value of the function is 100. The initial value is positive because the percentage of remaining battery life cannot be negative.

part d = The rate of change is the rate at which the y-value changes with respect to a change in the x-value. When off the charger, the phone loses its battery life at a constant rate of 5 percent per hour. So, the function’s rate of change is -5. The rate of change is negative because the rate indicates that the percentage of remaining battery life decreases as the number of hours increases.

part e = The rate of change of the function, m, is -5, and the initial value of the function, b, is 100. Substitute the values of m and b in the equation y = mx + b. The equation of the function that models the phone’s remaining battery life in terms of the number of hours from the time Vicky took it off the charger is y = -5x + 100.

Step-by-step explanation:

All edmentum answers :)

The estimate obtained from a sample of which of the following sizes would most likely be closest to the actual parameter value of a population?

Answers

To obtain an estimate of a parameter of a population, we use confidence intervals.

Confidence intervals:

The larger the sample size, the closest the parameter estimate is to the value of the population, as the margin of error of confidence intervals is inversely proportional to the sample size, that is, a greater sample leads to a smaller margin of error.

Thus, you should select the highest sample size in the options.

For more on confidence interval/margin of error, you can check https://brainly.com/question/22718960

please help me
its urgent :)

Answers

Step-by-step explanation:

i Will help wit Shape A and Next Try to figure out Shape B

shape A Looks the Shape XY coordinate, which Horizontal & Vertical Line

Shape A Coordinate

X = 7, 8.5, 7,5, 7.5,

Y = 7, 7, 6.5 , 5

if you wanna to understand this coordinate between X & Y try plotting with Horizontal or Vertical Line at your Shape And you Would be Understanding about these coordinate meaning

tan30°+cos30°÷tan30°×cos30°​

Answers

Answer:

{1/√3+1/2} ÷{1/√3× 1/2}

(2+√3)/2√3÷(1/2√3)2+√3+1 /2√3(2+1 )+√3 /2√33 +√3 /2√3

One of the legs of a right triangle measures 12 cm and its hypotenuse measures 20
cm. Find the measure of the other leg. If necessary, round to the nearest tenth.
Answer:
cm
Submit Answer
attempt 1 out of 2
PLS HELP

Answers

Answer:

16

Step-by-step explanation:

First use the Pythagorean theorem a^2+b^2=c^2.

12^2+b^2=20^2. Solve the exponents: 144+b^2=400. Then, subtract the 144 from 400. That would be 256. Therefore b^2=256. Then you find the square root of 256=16.

Step-by-step explanation:

using pythogoras theory

hyp^2=opp^2+adj^2

you have been given the hyp and the opp so lets make the unknown x

20^2=12^2+x^2

400 =144+x^2

make x the subject of the formula

400-144=x^2

266=x^2

x=the square root of 266

take a square of arbitary measure assuming its area is one square unit.divide it in to four equal parts and shade one of them.again take one shaded part of that square and shade one fourth of it.repeat the same process continuously and find the sum area of shaded region​

Answers

Answer:

In recreational mathematics, a square array of numbers, usually positive integers, is called a magic square if the sums of the numbers in each row, each column, and both main diagonals are the same.[1][2] The order of the magic square is the number of integers along one side (n), and the constant sum is called the magic constant. If the array includes just the positive integers {\displaystyle 1,2,...,n^{2}}{\displaystyle 1,2,...,n^{2}}, the magic square is said to be normal. Some authors take magic square to mean normal magic square.[3]

The smallest (and unique up to rotation and reflection) non-trivial case of a magic square, order 3

Magic squares that include repeated entries do not fall under this definition and are referred to as trivial. Some well-known examples, including the Sagrada Família magic square and the Parker square are trivial in this sense. When all the rows and columns but not both diagonals sum to the magic constant we have semimagic squares (sometimes called orthomagic squares).

The mathematical study of magic squares typically deals with its construction, classification, and enumeration. Although completely general methods for producing all the magic squares of all orders do not exist, historically three general techniques have been discovered: by bordering method, by making composite magic squares, and by adding two preliminary squares. There are also more specific strategies like the continuous enumeration method that reproduces specific patterns. Magic squares are generally classified according to their order n as: odd if n is odd, evenly even (also referred to as "doubly even") if n is a multiple of 4, oddly even (also known as "singly even") if n is any other even number. This classification is based on different techniques required to construct odd, evenly even, and oddly even squares. Beside this, depending on further properties, magic squares are also classified as associative magic squares, pandiagonal magic squares, most-perfect magic squares, and so on. More challengingly, attempts have also been made to classify all the magic squares of a given order as transformations of a smaller set of squares. Except for n ≤ 5, the enumeration of higher order magic squares is still an open challenge. The enumeration of most-perfect magic squares of any order was only accomplished in the late 20th century.

Magic squares have a long history, dating back to at least 190 BCE in China. At various times they have acquired occult or mythical significance, and have appeared as symbols in works of art. In modern times they have been generalized a number of ways, including using extra or different constraints, multiplying instead of adding cells, using alternate shapes or more than two dimensions, and replacing numbers with shapes and addition with geometric operations.

The sum area of shaded region​ is [tex]\frac{1}{3}[/tex].

Summation formula for geometric progression

The formula to find the sum of infinite geometric progression is

[tex]S_{n}=\frac{a_{1}(1-q^{n}) }{1-q} \ \ q \ne 1[/tex]

Given

S = [tex]\frac{1}{4} +\frac{1}{16} +\frac{1}{64} +.........[/tex]

Using geometric progression

S = [tex]\lim_{h \to \infty} [\frac{1}{4} +(\frac{1}{4} )^{2} +(\frac{1}{4} )^{3} +.........+(\frac{1}{4} )^{n}][/tex]

Using summation formula for geometric progression

[tex]S_{n}=\frac{a_{1}(1-q^{n}) }{1-q} \ \ q \ne 1[/tex]

= [tex]\lim_{h \to \infty} \frac{\frac{1}{4} (1-(\frac{1}{4} )^{n} }{1-\frac{1}{4} }[/tex]

= [tex]\lim_{h \to \infty} \frac{\frac{1}{4} (1-\frac{1}{4^{n} }) }{\frac{3}{4} }[/tex]

= [tex]\lim_{h\to \infty} \frac{1}{3}(1-\frac{1}{4^{n} } )[/tex]

[tex]\lim_{h\to \infty} \frac{1}{4^{n} }[/tex] = 0

S  = [tex]\frac{1}{3}(1-0) = \frac{1}{3}[/tex]

The sum area of shaded region​ is [tex]\frac{1}{3}[/tex].

Find out more information about summation formula for geometric progression here

brainly.com/question/27438806

#SPJ2

what value of x is in the solution set of -5-15>10+20x

Answers

Answer:

-3/2 >x

Step-by-step explanation:

-5-15>10+20x

Combine like terms

-20 > 10 +20x

Subtract 20 from each side

-20 -10 > 10+20x-10

-30> 20x

Divide by 20

-30/20 >20x/20

-3/2 >x

Answer:

-3/2 > x

Step-by-step explanation:

-5 - 15 > 10 + 20x

 ^    ^

  -20

-20 > 10 + 20x

-10    -10

---------------------

-30 > 20x

-----   -------

20     20

-3/2 > x

Hope this helped.

(84)/(12)+(5-7)^(2)-72-6x2

Answers

Answer:

[tex]-73[/tex]

Step-by-step explanation:

Note: My explanation is based of the order-of-operations

First, using the order-of-operations, we evaluate the expressions in parentheses. Fully simplifying [tex](5-7)^2[/tex] gives us: [tex](5-7)^2 = -2^2 = 4[/tex].

Next, we do [tex]6\cdot2[/tex] giving us [tex]12[/tex]. So far, our expression is simplified to [tex]\frac{84}{12} + 4 - 72 - 12[/tex].

We also know that [tex]\frac{84}{12}[/tex] is just [tex]7[/tex] so we can replace that value in the expression leaving us with: [tex]7+4-72-12[/tex]. Now, we can solve it in simple steps!

1)  [tex]7+4=11[/tex]

3) [tex]11-72=-61[/tex]

4) [tex]-61-12=-73[/tex]

Our answer is [tex]-73[/tex]

Hopefully this helped you out! Please (please) tell me if their is a mistake in the solution and I will correct it as fast as possible for me.

When a weed solution is added to a lawn, the number of weeds can be represented by the function W(d)=1500(.75)^d where d is the number of days since application. By what percent does the population of weeds decrease each day

Answers

Number of weeds is represented by the function,

[tex]W(d)=1500(0.75)^d[/tex]

[tex]W(d)=1500(1-0.25)^d[/tex] -------(1)

Here, [tex]d=[/tex] Number of days since application

Function representing the exponential decay is,

[tex]A(t)=A(1-r)^t[/tex] --------(2)

[tex]A=[/tex] Initial value

[tex]r=[/tex] Percentage decay

[tex]t=[/tex] duration

By comparing both the functions (1) and (2),

[tex]r=[/tex] 0.25 ≈ [tex]\frac{25}{100}[/tex]

Or [tex]r=[/tex] 25%

Therefore, population of weeds will decrease 25% each day.

Learn more about exponential decay,

https://brainly.com/question/14355665?referrer=searchResults

can someone pls help w finding the x and y intercepts of this?

y=x^2-2x

Answers

Answer:

y-intercept is 0, x-intercept is 0 and 1

Step-by-step explanation:

For y-intercept, x=0 :

[tex]{ \tt{y = {(0)}^{2} - 2(0) }} \\ { \tt{y = 0}}[/tex]

For x-intercept, y=0 :

[tex]{ \tt{0 = {2x}^{2} - 2x }} \\ { \tt{2x(x - 1) = 0}} \\ { \tt{x = 0 \: \: and \: \: 1}}[/tex]

Which inequality is represented by this graph?

OA. y<-1/5x+1
OB. y>= -1/5x+1
OC. y<= -1/5x+
OD. y>-1/5x+1​

Answers

Answer:

Option A is correct

Step-by-step explanation:

Hope it is helpful....

Find m so that the equation msin²x+cos²x=m-1 has a solution on the interval (0;π/4)​

Answers

msin²x+cos²x=m-1

since the interval are 0 and π/4

Therefore

msin²(0)+cos²(0)=m-1

m(0)+1=m-1

1=m-1

m=2

use π/4 now

msin²(π/4)+cos²(π/4)=m-1

m(1/2)+(1/2)=m-1

m+1=2(m-1)

m+1=2m-2

-m=-3

m=3

Therefore

m=2 or 3

help please help......​

Answers

Answer:

[tex]{ \sf{( \sec \theta - \csc \theta)(1 + \tan \theta + \cot \theta) }} \\ = { \sf{( \sec \theta + \tan \theta \sec \theta + \cot \theta \sec \theta) - ( \csc \theta - \csc \theta \tan \theta - \csc \theta \cot \theta)}} \\ = { \sf{( \sec \theta + \sec \theta \tan \theta + \csc \theta) - ( \csc \theta - \sec \theta - \csc \theta \cot \theta)}} \\ = { \sf{ \sec \theta \tan \theta + \csc \theta \cot \theta }} \\ { \bf{hence \: proved}}[/tex]

find the angle measures given the figure is a rhombus.​

Answers

Answer:

92

Step-by-step explanation:

180-88

Question choices:
A: I, IV

B: II, III, IV

C: III, IV

D: II, III

Answers

0Answer:

A

Step-by-step explanation:

Find the zeros by letting y = 0 , that is

x² - x - 6 = 0 ← in standard form

(x - 3)(x + 2) = 0 ← in factored form

Equate each factor to zero and solve for x

x - 3 = 0 ⇒ x = 3

x + 2 = 0 ⇒ x = - 2

Since the coefficient of the x² term (a) > 0

Then the graph opens upwards and will be positive to the left of x = - 2 and to the right of x = 3 , that is in the intervals

(-∞, - 2) and (3, ∞ ) → option A

divide 12by8 and 4by3​

Answers

12by8=1.5 4by3=1.3 1.5by1.3=1.12
Other Questions
Solid waste material from waste water is called A basketball player averages 22.5 points scored per game with a standard deviation of 6.2 points. In one game, the athlete scored 10 points. What is the z-score for the points scored in this game?2.021.631.632.02 If your listening preference is to "cut to the chase" by getting to the point quickly,then you are a(n) ______ listener.O people-orientedemotion-orientedaction-orientedcontent-oriented s the function represented by the table non-linear?xy64728092 What is species definition Forma oraciones completas usando los elementos. Usa el presente Del indictivo para el primer verbo y haz otros cambios que seran necesarios Condensation is the process of ____________________.a. planetesimals accumulating to form protoplanets.b. planets gaining atmospheres from the collisions of comets.c. clumps of matter adding material a small bit at a time.d. clumps of matter sticking to other clumps.e. clouds formed from volcanic eruptions. Lainey is looking for a new apartment and her realtor keeps calling her with new listings . The calls only take a few minutes , but a few minutes here and there are really starting to add up . She's having trouble concentrating on her work . What should Lainey do ? a ) Tell her realtor she can only receive text messages b ) Limit the time spent on each call c ) Turn off her phone until she is on a break d ) Call her realtor back when customers won't see her on the phone urgent help please just guess Mosquitoes are small flying insects which are very harmful. It is only female mosquitoes that bite people. Male mosquitoes do not consume blood.Blood serves as a source of protein for their eggs.can anyone suggest a title please and do not suggest introduction please A bacterial cell wall is composed of: A) A polysaccharide consisting of a single type of monosaccharide unit and cross-linking oligopeptides. B) A polysaccharide consisting of 2 types of monosaccharide units and cross-linking oligopeptides. C) A polysaccharide consisting of 3 types of monosaccharide units and cross-linking oligopeptides. D) Two different polysaccharides and 1 type of oligopeptide, which are cross-linked. What should I write? The energy required to change the state of a substance was determined to be E(H). If the mass of the substance was DOUBLED, the value of E(H) will(A) be halved (B) be doubled (C) be quadrupled (D) remain constant On a map, 1 in represents 420 miles. How much does 3/4 in represent? The Cell-mediated response is a chain reaction of antigens and Interleukins that results in:A. The swelling of fluid and clotting elements to a damaged area.B. The differentiation of helper T cells into cytotoxic T cells to destroy pathogens.C. The production of macrophages to use phagocytosis on pathogens.D. The differentiation of effector B cells into plasma cells to make antibodies. What is the role of a design tWhat is the role of a design tool in a Robotic Process Automation (RPA) solution? What is a similarity between the temperate climate zone and polar climate zone?A. Both climate zones get less than 100 cm of precipitation in a year.B. Both climate zones have average yearly temperature of around 25C.C. The polar and temperate climate zones have hot and dry summers.D. They have hot summers and cold winters because they are close to the ocean. Factorize this and solve no p, q, s, t, w John House has taken a 20-year, $250,000 mortgage on his house at an interest rate of 6 percent per year. What is the remaining balance (or value) of the mortgage after the payment of the fifth annual installment? A student graphs power (p) on the vertical axis and time (t) on the horizontal axis. The graph appears to be a hyperbola.a) What should the student graph on each axis to test whether the relationship is actuallyhyperbolic?b) If the relationship is actually hyperbolic, what is the general equation for the relationship between power and time? The quotient of -8 and the sum of a and b