Question

If y is directly proportional to x2 and y=365 when x=18, find y if x=9. (Round off your answer to the nearest hundredth.)

Answer 1

am going to assume you meant, y is directly proportional to x2

directly proportional means is that y equals x2 times some constant value, we will call "k".

y = kx2

We are given: y = 365 when x = 15
So we can solve for k.

365 = k(15)2
365 = 225k
k = 1.62

y = 1.62x2

find y if x = 10

y = 1.62(10)2
y = 162