Question

I don’t understand how to do this without plugging in numbers or using calculus. Please help. I’m studying for the SAT and I only know how to solve with calculus.

Answer 1

Explanation:

Recall that for a quadratic equation y = ax² + bx + c in the X-Y plane, the x-location of the vertex (i.e maximum or minimum point) is given by

x @vertex = -b/2a

in this case your quadratic equation is

h = 4 + 20t - 5t² (rearranging in the form y = ax² + bx + c )

h = - 5t² + 20t + 4

hence a= -5, b = 20 and c = 4

applying the formula for vertex

t @ vertex = -b /2a = -(20) / (2)(-5) = -20/-10 = 2

therefore t = 2