Question

A boy throws a baseball across a field. The ball reaches its maximum height, 18 meters, after 1 second. After approximately 2.3 seconds, the ball lands on the ground. The ball’s motion can be modeled using the function f(x) = –10x2 + 20x + 8. What is the height of the ball 1.5 seconds after it is thrown?

Answer 1

height is 15.5 meters

Answer 2

So we're looking to find the value of y in this case, or f(x) rather.

If f(x) = -10x^2 +20x +8, we input the number 1.5 as x, because we're looking for the height in relation to the seconds: y according to x. Thus:

f(x) = -10(1.5^2) +20(1.5) +8
f(x) = -10(2.25) +30 +8
f(x) = -22.25 +38
f(x) = 15.5m

You can also use desmos graphing calculator to check your work afterwards, bu this should solve your question.