Question

If y varies directly as x2 and y = 144 when x = 4, what is the value of y when x = -5?

a. -225
b. 225
c. 180
d. -180

Answer 1

y varies with x² times a constant. We will call the constant a
144=ax²
144 = a(4²)
144 = 16a
a = 9
Apply our equation y = 9x²
y = 9(-5)²
y = 9* 25
y=225
Answer is B