The quadratic function d = –3x2 + 16 models a skateboarder’s distance, in feet, from the bottom of a hill x seconds after the skateboarder starts moving down the hill.

Question

After how many seconds is the skateboarder 8 ft from the bottom of the hill?

Here are the answer choice:

A. 3.6s

B. 2.6s

C. 1.6s

D. 0.6s

Answer 1

To find the solution, plug in 8 for d

d=-3x²+16

8=-3x²+16 Subtract 8 from both sides

0=-3x²+8

Now, use the quadratic equation to solve for x

a=-3

b=0

c=8

x=1.63 or

C. 1.6s