If y varies directly as x and y = 3 when x = - 9, then find x when y = 5.
a. 15
b. 1/15
c. - 1 / 15
d. - 15

d. - 15

Step-by-step explanation:

The equation for direct variation is

y = kx

We know y =3 when x = -9

3 = k(-9)

Divide by -9

3/-9 = -9k/-9

-1/3 = k

The equation is then

y = -1/3 x

We know y = 5

5 = -1/3 x

Multiply each side by -3

-3*5 = -3*-1/3x

-15 = x

you need to show us the graph.

step-by-step explanation:

x = -3

y = -18

step-by-step explanation:

to solve by substitution, substitute one variable and solve for the other. then substitute again to find the remaining variable.

x-1/3(3x-9) = -3 since y=3x-9 substittute y.

x-1/3(3x-9)=-3

x + x +3 = -3

2x+3=-3

2x+3-3= -3-3

2x=-6

x=-3

substitute again into y=3x-9

y=3(-3)-9

y=-9-9

y=-18