Question

Y is directly proportional to x^2
If y = 8 when x = 2
find x when y = 32

Answer 1

4 or -4

Explanation:

Y is directly proportional to x^2 means there is a constant, k, such that y=kx^2.

We are given y=8 when x=2. This information will allow us to find k in the equation y=kx^2.

8=k(2)^2

8=k(4)

This implies k=2 since 2(4)=8.

So the equation for any pair (x,y) is y=2x^2.

We want to find x when y=32.

32=2x^2

32/2=2x^2/2

16=x^2

This implies x=4 or -4.