Question

A diver jumps into a pool from a board ten feet above the surface of the water. Her height, h, at any time t seconds after jumping is given by the equation h=tsquared-8t+10. What is the minimum height that she reaches? (Note: Negative values of h mean the diver is below the water.)
 
 
A. –26 feet
 
B. –10 feet
 
C. –6 feet
 
D. –4 feet

Answer 1

The parabola h = t^2 - 8t + 10 opens upward, so its minimum is at the vertex t = -b/(2a) = 8/2 = 4.
h(4) = 4^2 - 8·4 + 10 = 16 - 32 + 10 = -6.

Answer: C (−6 feet).