# Math

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The equation y=-4.9t^2+3.5t+5 describes the height (in meters) of a ball thrown upward at 3.5 meters per second from 5 meters above the ground. In how many seconds will the ball hit the ground? Express your answer as a common fraction.

• Math -

the ball hits the ground when y=0.

If you want a fraction, then let's get rid of the decimals:

y = 1/10 (-49t^2 + 35t + 50)
= 1/10 (7t+5)(10-7t)

y=0 when t = 10/7

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