SOLUTION: A baseball is thrown straight upward with an initial speed of 160 ft/sec. The number of feet s above the ground after t seconds is given by the equations = −16t^2 + 160t.(a)

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Question 989291: A baseball is thrown straight upward with an initial speed of 160 ft/sec. The number of feet s above the ground after t seconds is given by the equations = −16t^2 + 160t.(a) When will the baseball be 256 feet above the ground? (Enter your answers as a comma-separated list.)
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
+s+=+-16t%5E2+%2B+160t+
Here's the plot:
+graph%28+400%2C+400%2C+-2%2C+12%2C+-20%2C+450%2C+-16x%5E2+%2B+160x+%29+
----------------
Find +t+ when +s+=+256+
+256+=+-16t%5E2+%2B+160t+
+-16t%5E2+%2B+160t+-+256+=+0+
Divide both sides by +-16+
+t%5E2+-+10t+%2B+16+=+0+
+%28+t+-+2+%29%2A%28+t+-+8+%29+=+0+
+t+=+2+
+t+=+8+
The baseball is 256 above ground at
2 sec ( on the way up ) and at
8 sec ( on the way down )