if Y is directly proportional to X^2 and the difference in the values of Y when X=1 and X=3 is 32, find the value of Y when X=negative 2.

Question

this question is about direct proportion. 

Answer 1

y is directly proportional to x²

y = kx²

 

The difference in values of y when x=1

and x=3 is 32

k(3²) -  k(1²) = 32

9k - k = 32

8k = 32

k = 4

 

Your direct proportion is:

y = 4x²