A football is kicked into the air from an initial height of 4 feet. The height, in feet, of the football above the ground is given by s(t)=-16t^2+50t+4, where t is time, in sevonds, and t \= 0. At what time will the football be 25 feet above the ground?

Question

A football is kicked into the air from an initial height of 4 feet. The height, in feet, of the football above the ground is given by s(t)=-16t^2+50t+4, where t is time, in sevonds, and t >\= 0. At what time will the football be 25 feet above the ground?

anonymous · Answer

A. 3.625 seconds 
B. 3.20 seconds
C. .5 seconds or 3.625 seconds
D. .5 seconds or 2.625 seconds

loser66 · Answer

your idea?

anonymous · Answer

set s(t) = 25 and solve

anonymous · Answer

I don't think this equation would have two solutions, so C and D are not correct, right?

loser66 · Answer

why do you say so? it's a quadratic and its graph is a parabola, the time t can be 2 values , one when the ball  up and one down

anonymous · Answer

But since time cant be negative then we would only have 1. And 25 would be the max so it would be only one point with the parabola opening down

loser66 · Answer

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anonymous · Answer

it's possible but arent we using 25 as the max?

loser66 · Answer

to me, I would solve as souring suggested. I would not reject the option at the beginning.

loser66 · Answer

what makes you think 25 is max height?

anonymous · Answer

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loser66 · Answer

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