Which equation describes a relationship that is directly proportional? (A) y = 9
(B) y = 1/5
(C) y = 3x
(D) y = x + 4

(C) y = 3x

Step-by-step explanation:

Directly proportional relation is one in which the value of x and y gets increases or decreased in same proportion.

example of such relation can be y = kx

where k is the constant of proportionality which depicts by how much value of  y will change in response to change of x.

now in the option

A and B

y= 9 , y =1/5

value of y is constant and does not depend on other variable. it value will remain same.

for y = x+4

value of y increases with x but it does not increase proportionally.

let see an example for x =1 , y = 1+4 = 5

x =2 , y = 2+4 = 6

(1,5)  and (2,6) are not proportionally changing also this equation is not of form y = kx

thus, it is incorrect option.

(C) y = 3x

here equation is form y =kx .  in place of k there is 3

let see an example for x =1 , y = 3*1 = 3

x =2 , y = 3*2 = 6

(1,3)  and (2,6) are  proportionally changing (1/3 = 2/6) also this equation is  of form y = kx

thus, it is correct option.

98%

step-by-step explanation:

b. y = 4x - 2

step-by-step explanation:

to find a parallel equation to an equation, make sure both equations have the same slope but different y-intercepts.

y = 4x + 1

4 = slope

1 = y-intercept

y = 4x - 2

4 = slope

-2 = y-intercept

they both have the same slope but different y-intercepts, so, b. is the correct answer.

and to check your work, you can graph both equations. : )