Question

If y varies directly as x^2 and y = 144 when x = 4, what is the value of y when x = -5?

Answer 1

As the variation is direct then we have the following expression:
 $y = kx ^ 2$
 From here, we clear the value of k.
 For this we use the following data:
 y = 144 when x = 4
 Substituting values:
 $144 = k4 ^ 2$
 Clearing k we have:
 $k = 144/4 ^ 2 k = 144/16 k = 9$
 Then, the function is:
 $y = 9x ^ 2$
 When x = -5 we have:
 $y = 9 (-5) ^ 2 y = 9 (25) Y = 225$
 Answer:
 the value of y when x = -5 is:
 b.
 225