Answer:
P (x= 5) = 0.0001
P(x=3) = 0.008699
Step-by-step explanation:
This is a binomial distribution .
Here p = 0.8 q= 1-p = 1-0.8 = 0.2
n= 15
So we find the probability for x taking different values from 0 - 15.
The formula used will be
n Cx p^x q^n-x
Suppose we want to find the value of x= 5
P (x= 5) = 15C5*(0.2)^10*(0.8)^5 = 0.0001
P(x=3) = 15C3*(0.2)^12*(0.8)^3 = 9.54 e ^-7= 0.008699
Similarly we can find the values for all the trials from 0 -15 by substituting the values of x =0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15.
The value for p(x = 5) is 0.0001 and the value for p(x = 3) is 0.008699.
It is given that the 80% of all brand A external hard drives work in a satisfactory manner throughout the warranty period.
It is required to find the sampling distribution if n =15 samples.
What is sampling distribution?It is defined as the probability distribution for the definite sample size the sample is the random data.
We have p =80% = 0.8 and q = 1 - p ⇒ 1 -0.8 ⇒ 0.2
n = 15
We can find the probability for the given x by taking different values from 0 to 15
the formula can be used:
[tex]\rm _{n}^{}\textrm{C}_x p^xq^{n-x}[/tex]
If we find the value for p(x = 5)
[tex]\rm _{15}^{}\textrm{C}_5 p^5q^{15-5}\\\\\rm _{15}^{}\textrm{C}_5 0.8^50.2^{10}[/tex]⇒ 0.0001
If we find the value for p(x = 3)
[tex]\rm _{15}^{}\textrm{C}_3 0.8^30.2^{12}\\[/tex] ⇒
Similarly, we can find the values for all the trials from 0 to 15 by putting the values of x = 0 to 15.
Thus, the value for p(x = 5) is 0.0001 and the value for p(x = 3) is 0.008699.
Learn more about the sampling distribution here:
https://brainly.com/question/10554762
Which of the following correlation values represents a perfect linear relationship between two quantitative
variables? Select all that apply.
A. 0
B. 9
c. -1
D. 1
E. .5
Answer:
C. -1
D. 1
Step-by-step explanation:
A perfect linear relationship is indicated by a correlation with a magnitude of 1. The sign of the correlation coefficient is the sign of the slope of the line describing the relationship. It may be positive or negative.
The appropriate choices are ...
C. -1
D. 1
Answer:
c=-1
d=1
Step-by-step explanation:
A passenger train traveled 180 miles in the same amount of time it took a freight train to travel 120 miles. The rate of the freight train was 15 miles per hour slower than the rate of the passenger train. Find the rate of the passenger train.
Answer:
The passenger train is moving at 45 miles per hour
Step-by-step explanation:
Let the amount of time it took the two trains to travel the distance = t.
Since the two trains traveled the distance at the same time,
Rate of the passenger train =[tex]\frac{180}{t}[/tex]
Rate of the freight train = [tex]\frac{120}{t}[/tex]
Where t is in hours.
From the problem, we can see that the rate of the freight train was 15 miles per hour slower than the rate of the passenger train. Mathematically, we can represent this as
[tex]\frac{120}{t}= \frac{180}{t}-15[/tex]
from the above equation, we can now get our value for t as
[tex]\frac{120-180}{t}=-15\\\frac{-60}{t}=-15\\t=4 hours[/tex]
We have our time of travel for the two trains as 4 hours.
The rate of the passenger train can now be calculated by 180/4 = 45 miles per hour
The cost of performance tickets and beverages for a family of four can be modeled using the equation 4x+12=48,where x represents the cost of a. Ticket.how much is one ticket
Answer:
x=9; one ticket is $9
Step-by-step explanation:
4x+12=48
4x=48-12
4x=36
x=36/4
x=9
The half-life of a radioactive isotope is the time it takes for a quantity of the isotope to be reduced to half its initial mass. Starting with 220 grams of a radioactive isotope, how much will be left after 5 half-lives?
Answer:
[tex]\boxed{6.875 \text{\: grams}}[/tex]
Step-by-step explanation:
Half-lives are how long it takes for half of a substance to decay. If you start with a certain amount and it decays for a certain amount of half-lives, you are dividing by [tex]2^{x}[/tex], where x is equal to the amount of half-lives.
In order to solve this question, simply divide the starting value by 2 raised to the value of half-lives.
[tex]\large\boxed{\frac{220}{2^{5}}=6.875\text{\: grams}}[/tex]
2 1/2 cases of soda to split between 5 families
The fraction that each person gets is 1/2.
How to compute the fraction?It should be noted that 2 1/2 cases of soda to split between 5 families.
In their case, the fraction that each person will get will be:
= Total / Number of people
= 2 1/2 ÷ 5
= 2.5/5
= 0.5 or 1/2.
Learn more about fractions on:
brainly.com/question/17220365
#SPJ1
2 1/2 cases of soda to split between 5 families. What fraction will each person get?
In tests of a computer component, it is found that the mean time between failures is 520 hours. A modification is made which is supposed to increase the time between failures. Tests on a random sample of 10 modified components resulted in the following times (in hours) between failures. 518 548 561 523 536 499 538 557 528 563 At the 0.05 significance level, test the claim that for the modified components, the mean time between failures is greater than 520 hours. Use the P-value method of testing hypotheses.
H0:
H1:
Test Statistic:
Critical Value:
Do you reject H0?
Conclusion:
If you were told that the p-value for the test statistic for this hypothesis test is 0.014, would you reach the same decision that you made for the Rejection of H0 and the conclusion as above?
Answer:
As the calculated value of t is greater than critical value reject H0. The tests supports the claim at ∝= 0.05
If the p-value for the test statistic for this hypothesis test is 0.014, then the critical region is t ( with df=9) for a right tailed test is 2.821
then we would accept H0. The test would not support the claim at ∝= 0.01
Step-by-step explanation:
Mean x`= 518 +548 +561 +523 + 536 + 499+ 538 + 557+ 528 +563 /10
x`= 537.1
The Variance is = 20.70
H0 μ≤ 520
Ha μ > 520
Significance level is set at ∝= 0.05
The critical region is t ( with df=9) for a right tailed test is 1.8331
The test statistic under H0 is
t=x`- x/ s/ √n
Which has t distribution with n-1 degrees of freedom which is equal to 9
t=x`- x/ s/ √n
t = 537.1- 520 / 20.7 / √10
t= 17.1 / 20.7/ 3.16227
t= 17.1/ 6.5459
t= 2.6122
As the calculated value of t is greater than critical value reject H0. The tests supports the claim at ∝= 0.05
If the p-value for the test statistic for this hypothesis test is 0.014, then the critical region is t ( with df=9) for a right tailed test is 2.821
then we would accept H0. The test would not support the claim at ∝= 0.01
In a survey of 15000 students of different schools, 40% of them were found to have tuition before the see examination. Among them 50% studied only mathematics ,30% only science and 10% studied others subject. how many student studied mathematics as well as science.
Answer:
600
Step-by-step explanation:
first, 40% of 15000 is 6000,
10% of 6000, which is the number of students studying mathematics as well as science, 600
Answer:
•600 students studied both the subject.
Please help. I’ll mark you as brainliest if correct
Answer:
bonds: $65,000
cd's: $30,000
stocks: $20,000
Step-by-step explanation:
b + c + s = 115000
0.045b + 0.0325c + 0.082s = 5540
b = c + 35000
b = 65,000
c = 30,000
s = 20,000
Pls help me I promise I’ll mark u brainleiest if I type in the fastest answer
Answer:
1. $-50
2. $25
Step-by-step explanation:
1. If she had $150 in her bank account and bought a bike for $200, then that means she spent all of her money PLUS $50 extra then what she had. That means $200-$150=$50. Her $150 is spent and that $50 becomes negative because she paid $200 when she only had $150.
2. If she deposits $75 in her account then it will be $75+(-50). That translates to $75-$50 which is $25.
+ and - = -
+ and + = +
- and - = +
Answer:
1. $-50
2. $25
Step-by-step explanation:
1.
We know that Clare originally had $150 in her account. She then buys a bike, which means she must have taken money out of her account for this purchase.
Since she spent $200, we need to subtract 200 from 150:
150 - 200 = -50
So, her account balance is $-50.
2.
Clare earns $75 later, which means she's receiving the money and can add it back into her account. Her current balance is -50, so we add 75 to -50:
-50 + 75 = $25
Thus, her account balance is now $25.
~ an aesthetics lover
Kent Co. manufactures a product that sells for $60.00. Fixed costs are $285,000 and variable costs are $35.00 per unit. Kent can buy a new production machine that will increase fixed costs by $15,900 per year, but will decrease variable costs by $4.50 per unit. What effect would the purchase of the new machine have on Kent's break-even point in units?
0riginal break even point:
285000/ 60/35 = $166,250
New break even point = new fixed costs / ( selling price - variable cost/ selling price)
New break even point = 285,000 + 15,900. / ( 60-( 35-4.50)/60
300,900 / 60-30.50/60 = $612,000
The new break even point increases.
Help me please thank you
Answer: 60°
Step-by-step explanation:
apply concept: the interior angle sum of triangle is 180°
x+x+x=180
3x=180
x=60
---------------
this is also an equilateral triangle which if you know it, you will know that each angles are all 60°
Answer: x=60°
Step-by-step explanation:
We know that the sum of the angles in a triangle is 180°. Since all of the angles are x°, we know that they are equal in degrees. Since there are 3x, we can use that to solve for x.
3x=180 [divide both sides by 3]
x=60°
Multiple Choice The opposite of –4 is A. 4. B. –4. C. –(–(–4)). D. –|4|.
Answer:
a. 4
Step-by-step explanation:
-1(-4) = 4
Answer:
A 4
Step-by-step explanation:
opposite of –4 = 4
Use any estimation strategy to calculate ,51.12 times 87.906 pls help!
Answer:
the real answer is: 4493.75472
BUT for ESTIMATION STRATEGY it is: 4500
Step-by-step explanation:
Please help me!!Which of the following functions shows the linear parent function, Fx) = X,
shifted right?
5
F(x) = x
5
A. G(x) = x + 2
B. G(x) = 4x
C. G(x) = x - 9
D. G(x) = -x
Answer:
C. G(x) = x - 9
Step-by-step explanation:
You know that the transformation ...
g(x) = f(x -h) +k
causes parent function f(x) to be shifted right h units and up k units.
You're looking for a function that is shifted right, so you want something that looks like ...
g(x) = f(x -constant) = x - constant
Choice C has that form:
C. G(x) = x - 9
_____
A. the function is shifted up 2 units
B. the function is vertically expanded by a factor of 4 (no shift)
C. shifted right
D. the function is reflected over the y-axis (no shift)
Answer: C [G(x) = x-9]
Step-by-step explanation:
I got it right
Factor by grouping cd-9d-4c+36
Answer:
(d-4)(c-9)
Step-by-step explanation:
cd-9d-4c+36
d(c-9)-4(c-9)
pull out the (c-9),
(d-4)(c-9)
state if the triangles in each pair are similar. If so State how you know they are similar and complete the similarity statement
Answer:
fourth option
Step-by-step explanation:
∠ FTC = ∠ MTL ( vertical angles )
Since FC and ML are parallel, then
∠ FCT = ∠ TML (corresponding angles )
Thus
Δ TCF ~ Δ TML by the AA postulate
Answer:
[tex]\large \boxed{\mathrm{similar, \ AA \ similarity}, \ \Delta TML}[/tex]
Step-by-step explanation:
The two triangles are similar.
We can prove by angle-angle similarity, in [tex]\mathrm{AA}[/tex] similarity, there are two pairs of congruent corresponding angles in two triangles, this proves the two triangles are similar.
[tex]\angle U[/tex] and [tex]\angle M[/tex] are a pair of congruent corresponding angles.
[tex]\angle V[/tex] and [tex]\angle L[/tex] are a pair of congruent corresponding angles.
Therefore,
[tex]\Delta TUV \sim \Delta TML[/tex]
A rectangle has an area of 81 square centimeters. Which of the following would be the rectangle's length and width? (Area = equals length×times width)
Answer:
length: 9cm
width: 9cm
Step-by-step explanation:
9×9=81
[tex]f(x) = sqr root x+3 ; g(x) = 8x - 7[/tex]
Find (f(g(x))
[tex]f(x)=\sqrt{x+3}\\g(x)=8x-7\\\\f(g(x))=\sqrt{8x-7+3}=\sqrt{8x-4}[/tex]
3y – 6x = 3 y = 2x + 1
Answer:
infinite solutions along the line y = 2x+1
Step-by-step explanation:
3y – 6x = 3
y = 2x + 1
Replace y in the first equation with the second equation
3 ( 2x+1) -6x =3
6x +3 -6x = 3
3=3
This is always true so there are infinite solutions along the line y = 2x+1
Step-by-step explanation:
Hi, there!!!
you mean to solve it, right.
then let's begin...
3y-6x=3..........epuation 1.
y = 2x+1..........equation 2.
now, substituting the value y of equation 2 in equation 1. so, we get,
3y-6x=3
or, 3(2x+1) -6x = 3
or, 6x+3-6x=3
by simplifying it we get, 3=3
so, this equation can have infinite solution.
you may have wrote wrong question ..
Among a simple random sample of 331 American adults who do not have a four-year college degree and are not currently enrolled in school, 48% said they decided not to go to college because they could not afford school.
Part II: Exercise 6.16 presents the results of a poll where 48% of 331 Americans who decide to not go to college do so because they cannot afford it.
#1: Calculate a 90% confidence interval for the proportion of Americans who decide to not go to college because they cannot afford it, and interpret the interval in context.
(a) lower bound: ______ (please round to four decimal places)
(b) upper bound: _____ (please round to four decimal places)
#2: Interpret the confidence interval in context:
(A) We can be 90% confident that our confidence interval contains the sample proportion of Americans who choose not to go to college because they cannot afford it
(B) 90% of Americans choose not to go to college because they cannot afford it
(C) We can be 90% confident that the proportion of Americans who choose not to go to college because they cannot afford it is contained within our confidence interval
#3: Suppose we wanted the margin of error for the 90% confidence level to be about 1.5%. How large of a survey would you recommend?
(a) A survey should include at least ________ people.
Answer:
(1) Therefore, a 90% confidence interval for the proportion of Americans who decide to not go to college because they cannot afford it is [0.4348, 0.5252].
(2) We can be 90% confident that the proportion of Americans who choose not to go to college because they cannot afford it is contained within our confidence interval
(3) A survey should include at least 3002 people if we wanted the margin of error for the 90% confidence level to be about 1.5%.
Step-by-step explanation:
We are given that a simple random sample of 331 American adults who do not have a four-year college degree and are not currently enrolled in school, 48% said they decided not to go to college because they could not afford school.
Firstly, the pivotal quantity for finding the confidence interval for the population proportion is given by;
P.Q. = [tex]\frac{\hat p-p}{\sqrt{\frac{\hat p(1-\hat p)}{n} } }[/tex] ~ N(0,1)
where, [tex]\hat p[/tex] = sample proportion of Americans who decide to not go to college = 48%
n = sample of American adults = 331
p = population proportion of Americans who decide to not go to
college because they cannot afford it
Here for constructing a 90% confidence interval we have used a One-sample z-test for proportions.
So, 90% confidence interval for the population proportion, p is ;
P(-1.645 < N(0,1) < 1.645) = 0.90 {As the critical value of z at 5% level
of significance are -1.645 & 1.645}
P(-1.645 < [tex]\frac{\hat p-p}{\sqrt{\frac{\hat p(1-\hat p)}{n} } }[/tex] < 1.645) = 0.90
P( [tex]-1.645 \times {\sqrt{\frac{\hat p(1-\hat p)}{n} } }[/tex] < [tex]\hat p-p[/tex] < [tex]1.645 \times {\sqrt{\frac{\hat p(1-\hat p)}{n} } }[/tex] ) = 0.90
P( [tex]\hat p-1.645 \times {\sqrt{\frac{\hat p(1-\hat p)}{n} } }[/tex] < p < [tex]\hat p+1.645 \times {\sqrt{\frac{\hat p(1-\hat p)}{n} } }[/tex] ) = 0.90
90% confidence interval for p = [ [tex]\hat p-1.645 \times {\sqrt{\frac{\hat p(1-\hat p)}{n} } }[/tex] , [tex]\hat p+1.645 \times {\sqrt{\frac{\hat p(1-\hat p)}{n} } }[/tex] ]
= [ [tex]0.48 -1.96 \times {\sqrt{\frac{0.48(1-0.48)}{331} } }[/tex] , [tex]0.48 +1.96 \times {\sqrt{\frac{0.48(1-0.48)}{331} } }[/tex] ]
= [0.4348, 0.5252]
(1) Therefore, a 90% confidence interval for the proportion of Americans who decide to not go to college because they cannot afford it is [0.4348, 0.5252].
(2) The interpretation of the above confidence interval is that we can be 90% confident that the proportion of Americans who choose not to go to college because they cannot afford it is contained within our confidence interval.
3) Now, it is given that we wanted the margin of error for the 90% confidence level to be about 1.5%.
So, the margin of error = [tex]Z_(_\frac{\alpha}{2}_) \times \sqrt{\frac{\hat p(1-\hat p)}{n} }[/tex]
[tex]0.015 = 1.645 \times \sqrt{\frac{0.48(1-0.48)}{n} }[/tex]
[tex]\sqrt{n} = \frac{1.645 \times \sqrt{0.48 \times 0.52} }{0.015}[/tex]
[tex]\sqrt{n}[/tex] = 54.79
n = [tex]54.79^{2}[/tex]
n = 3001.88 ≈ 3002
Hence, a survey should include at least 3002 people if we wanted the margin of error for the 90% confidence level to be about 1.5%.
If the average fixed cost (AFC) of producing 5 bags of rice is $20.00, the average fixed cost of producing 10 bags will be
Answer:$40.00
Step-by-step explanation:first divide 20 by 5 and the answer will be 4. now multiply 10 into 4 and you'll get the answer $40.00
NEED HELP NOW I have 31 stamps total. I have 4 more 1-cent stamps than 8-cent stamps and twice as many one cent stamps as 12 cent stamps. If my stamps are worth $1.78 altogether how many one cent stamps do I have?
x = number of 1-cent stamps
y = number of 8-cent stamps
z = number of 12-cent stamps
We have 31 stamps all together, so x+y+z = 31.
"I have 4 more 1-cent stamps than 8-cent stamps" means we have the equation x = y+8. Whatever y is, add 8 to it to get x. Solve for y to get y = x-8.
You also have "twice as many one cent stamps as 12 cent stamps", so x = 2z. Solving for z gets you z = 0.5x
-------------
x+y+z = 31
x+x-8+z = 31 ... y replaced with x-8
x+x-8+0.5x = 31 ... plug in z = 0.5x
2.5x-8 = 31
2.5x = 31+8
2.5x = 39
x = 39/2.5
x = 15.6
Your teacher made a typo somewhere because we should get a positive whole number result for x (since x is a count of how many 1-cent stamps we have).
The number of one-cent stamps is 14.
Total stamps = 31
We have three types of stamps: 1-cent stamps, 8-cent stamps, and 12-cent stamps.
The person has 4 more 1-cent stamps than 8-cent stamps.
The person has twice as many 1-cent stamps as 12-cent stamps.
We have to make equations with the given above statement.
Consider,
1-cent stamp = A
8-cent stamp = B
12-cent stamp = C
4 more 1-cent stamps than 8-cent stamps: A = 4 + B.
A = 4 + B
B = A - 4..........(1)
Twice as many 1-cent stamps as 12-cent stamps: A = 2C.
A = 2C
C = A/2...............(2)
Total number of stamps = 31
A + B + C = 31................(3)
Putting (1) and (2) in (3)
we get,
A + ( A - 4 ) + A / 2 = 31
A + A - 4 + A / 2 = 31
2A - 4 + A / 2 = 31
2A + A / 2 = 31 + 4
(4A + A) / 2 = 35
4A + A = 35 x 2
5A = 70
A = 70 / 5
A = 14
Thus the number of 1-cent stamps is 14.
Learn more about similar problems here:
https://brainly.com/question/16959755
#SPJ5
Solve for x and y simultaneous equations: 2x+y=10
-3x+y=-5
Step-by-step explanation:
Hey, there!
Given, equations are,
2x+y=10.............(i)
-3x+y= -5...........(ii)
From equation (i)
y=10- 2x...........(iii)
Putting the value of "y" from equation (iii) in equation (ii).
-3x+y= -5
-3x + (10-2x)= -5
-3x + 10-2x= -5
- 5x = -15
[tex]x = \frac{ - 15}{ - 5} [/tex]
Therefore, x= 3.
Now, putting the value of "x" in equation (iii).
y= 10- 2x
y= 10- 2×3
Therefore, y= 4.
Hope it helps...
In your own words, define Quadratic Equation. How many solutions does a Quadratic Equation have?
Answer: an equation that has one term which is nameless and squared also no term which gets raised to higher power.
Step-by-step explanation:
Evaluate a + b for a = 12 and b = 6.
Answer:
Here,
a= 12
b = 6
Then,
a+b
= 12 + 6
= 18
.°. 18 is the solution
Answer:
[tex] \boxed{ \bold{ \boxed{ \sf{18}}}}[/tex]
Step-by-step explanation:
If the values of variables of algebraic expressions are given, the value of the term or expression can easily obtained by replacing the variables with numbers.
Given, a = 12 and b = 6
[tex] \sf{a + b}[/tex]
plug the values
⇒[tex] \sf{12 + 6}[/tex]
Add the numbers
⇒[tex] \sf{18}[/tex]
Hope I helped!
Best regards!!
Ernie Rolph borrowed $6700 at 4% annual simple interest. If exactly 1 year later he was able to repay the loan without penalty, how much interest would he owe? Ernie will owe $___ in interest.
Ernie will owe an interest of $268
From a group of 11 people, 4 are randomly selected. What is the probability the 4 oldest people in the group were selected
The probability that the 4 oldest people in the group were selected is based on combinatorics is 0.00303 or 0.303%.
Given that:
Find how many ways the 4 oldest people can be selected from the group.
Since the 4 oldest people are already determined, there is only 1 way to select them.
n = 11 (total number of people in the group) and k = 4 (number of people to be selected).To calculate the probability, to determine the total number of ways to select 4 people from the group of 11. This can be found using the combination formula:
Number of ways to choose k items from n items :
C(n,k) = n! / (k!(n-k)!)
Calculate the total number of ways to select 4 people from the group:
Plugging n and k value from given data:
C(11,4 )= 11! / (4!(11-4)!)
On simplifications gives:
C(11, 4) = 330.
Calculate the probability:
Probability = Number of ways 4 oldest people selected / Total number of ways to select 4 people
Plugging the given data:
Probability = 1 / 330
Probability ≈ 0.00303 or 0.303%.
Therefore, the probability that the 4 oldest people in the group were selected is based on combinatorics is 0.00303 or 0.303%.
Learn more about probabilities here:
https://brainly.com/question/23846068
#SPJ4
the height of a soccer ball that is kicked from the ground can be approximated by the function:
y = -12x^2 + 60x
where y is the height of the soccer ball in feet in x seconds after it is kicked. Find the time, in seconds, it takes from the moment soccer is kicked until it returns to the ground
Answer:
5 seconds
Step-by-step explanation:
Well we know that when the soccer ball is on the ground the height will be 0.
So we replace y with 0 and solve for x.
0=-12x²+60x
factor out and divide x, (this x is x=0, which is before he kicked it)
0=-12x+60
subtract 60 from both sides
-60=-12x
x=5
John painted his most famous work, in his country, in 1930 on composition board with perimeter 101.14 in. If the rectangular painting is 5.43 in. taller than it is wide, find the dimensions of the painting.
Answer:
22.57 x 28
Step-by-step explanation:
10.86 + 4x = 101.14
-10.86 -10.86
4x = 90.28
/4 /4
x = 22.57
5.43 + 22.57 = 28
22.57
Which of the following expressions represents a function? (5 points) a {(1, 2), (4, −2), (8, 3), (9, −3)} b y2 = 16 − x2 c 2x2 + y2 = 5 d x = 7
Answer: Option "a" is the only expression that represents a function.
Step-by-step explanation:
A function f(x) = y is a "operator" that takes an input element, x, and assigns it to only one output element, y.
So, if we have that for a given value of x.
f(x) = y and f(x) = h
where y and h are different values, then this is not a function, because is assigning the input value x to two different output values.
Let's see the different options:
a) {(1, 2), (4, −2), (8, 3), (9, −3)}
This points are of the form (x, y)
We can see that each value of x is assigned to only one value of y, so this can represent a function.
b) y^2 = 16 − x^2
Ok, suppose that x = 0, then:
y^2 = 16 - 0 = 16
then we have that y*y = 16.
So y can take two different values:
y = 4 ---> 4*4 = 16
y = -4 ---> -4*-4 = 16.
So this is not a function.
c) 2x^2 + y^2 = 5
First, we want to isolate y in one side:
y^2 = 5 - 2*x^2
Here we have a similar case to the option b, and we can use a similar argument to prove that this is not a function, so we can discard this.
d) x = 7.
Ok, this is not a relation between two variables, so this is not a function, as if x is the input value, we have only one value of x that solves the equation.
