The missing piece of the expression is 2
From the question, the height of the rocket above the ground in feet after t seconds is given by the function h(t) = -5t^2 + 20t -15
At maximum height, the velocity of the function is zero. Hence;
dh/dt - -5(2)t + 20
dh/dt = -10t + 20
Write the expression in vertex form as shown:
h(t) = -5t^2 + 20t -15
h(t) = -5(t^2 - 4t +3)
h(t) = -5(t^2 - 4t + 2^2 + 3 - 2^2)
h(t) = -5((t+2)^2 +5
h(t) = -5((t+2)^2 + 11
Hence the missing piece of the expression is 2
Learn more on vertex form here: https://brainly.com/question/525947