SOLUTION: Please help me solve this word problem: A ball is projected from the ground. Its distance in feet from the ground in t seconds is given by the equation s(t)=-16t+128t. At what t

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Question 136699: Please help me solve this word problem:
A ball is projected from the ground. Its distance in feet from the ground in t seconds is given by the equation s(t)=-16t+128t. At what times will the ball be 100 feet from the ground?
Answer by scott8148(6628) About Me  (Show Source):
You can put this solution on YOUR website!
you seem to be missing an exponent __ -16t should be -16t^2

put 100 in for s(t) and solve for t __ 100=-16t^2+128t __ 0=-16t^2+128t-100

dividing by -4 __ 0=4t^2-32t+25

use the quadratic formula to find the values of t