Question

y varies directly as the square of x. When x = 3, y = 54. Find y when x = 8 im not sure if its 384 or 144
y varies directly as the square of x. When x = 3, y = 54. Find y when x = 8 im not sure if its 384 or 144
@Mathematics

Answer 1

"y varies directly as the square of x" means that y = kx^2


When x = 3, y = 54, this mean is that


54 = k(3)^2


54 = k(9)


54 = 9k


54/9 = k


6 = k


k = 6


So the equation is y = 6x^2


Now when x = 8, y is...

y = 6x^2


y = 6(8)^2


y = 6(64)


y = 384


So when x = 8, y = 384