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Please help me....trying to get my HS diploma, i did not graduate :(

A ball is thrown in air and it's height, h(t) in feet, at any time, t in seconds, is represented by the equation h(t)=−t2+7t. When is the ball higher than 10 feet off the ground?

A. 2 B. −5≤t≤−2
C. 2≤t≤5
D. −5


Sagot :

When t is between 2 and 5, the ball will be above 10 feet.so answer is:

C. 2 ≤ t ≤ 5

Given, height h(t) = ₋t² ₊ 7t

At what values of time t is the ball 10 feet above the ground = ?

To find out the time we need to set up an inequality.

Inequality expression is given as = ₋t² ₊ 7t ≥ 10

                                                       = ₋t² ₊ 7t ₋ 10 ≥ 0

                                                       = ₋(t² ₋ 7t ₊ 10) ≥ 0

                                                       = t² ₋ 7t ₊10 ≥ 0

Now, factorize the expression and get the factors.

= t² ₋ 2t ₋ 5t ₊ 10 ≥ 0

=t(t ₋ 2) ₋ 5(t ₋ 2) ≥ 0

=(t ₋ 2) (t ₋ 5) ≥ 0

Hence t value ranges from t = 2 and 5.

As a result, when t is between 2 and 5 seconds, the ball will be farther than 10 feet, 2 ≤ t ≤ 5

Learn more about "Inequality equations" here-

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