The height, h, in meters, of a football t seconds after being thrown is given by the formula: #h = 30t - 5t^2#. How long after being thrown is the ball at a height of 25 meters?

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Answer 1 · 2017-11-24T21:32:38

Replace h with 25m.

# 25 = 30t - 5t^2 #

Rearrange it

# -5t^2 + 30t -25 = 0 #

Facotorization and Simplification

# -5 ( t^2 -6t + 5) = 5(t-5)(t-1)#

Find t

# (t-5)=0, t = 5#
# (t-1)=0, t = 1 #

Has a height of 25 at 1 s and 5 s