Question

y varies directly as the square of x. When x = 2, y = 40. Find x when y = 640.

x = ±6

x = ±8

x = ±12

x = ±20

Answer 1

it means y = k x^2 (for some constant k)
=> y1/y2 = (x1/x2)^2
here y1= 40,x1 =2
and y2 = 640, x2= ?

Answer 2

12?

Answer 3

try again..

Answer 4

8

Answer 5

yep..the very same ^_^
note its both 8 and -8

Answer 6

Ok, Thanks!