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 A rock is thrown upward from the height of 5 ft with an initial velocity of 50 ft per second. The height h(in feet) of the rock at time t seconds is h(t)=-16t^2+50t+5. When will the rock reach a height of 8 ft?

 Jul 9, 2021
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h(t) = 8  ft

 

8 = -16t^2 + 50t+5

-16t^2 + 50t -3   = 0       Use quadrtatic formula    a = -16    b = 50     c = -3       

                                                       you will get two values for 't' at 8 ft    one is going up     one is coming back down

                                                               obviously the smaller value will be the first time the rock reaches 8ft ...on the way up

 Jul 9, 2021

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