The height of a ball thrown into the air after t seconds have elapsed is h = −16t2 + 40t + 6 feet. What is the first time, t, when the ball will reach a height of 20 feet? Round your answer to two decimal places.

Solution:

Given that,

The height of a ball thrown into the air after t seconds have elapsed is:

What is the first time, t, when the ball will reach a height of 20 feet?

Substitute h = 20

Solve by quadractic formula

Rounding off we get,

t = 2.08 , t = 0.42

Thus the first time when the ball will reach a height of 20 feet is 0.42 seconds

step-by-step explanation:

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