SOLUTION: an object is thrown upward from the top of a 144-foot building with a initial velocity of 128 feet per second. The height h of the object after t seconds is given by the quadratic

Algebra ->  Rectangles -> SOLUTION: an object is thrown upward from the top of a 144-foot building with a initial velocity of 128 feet per second. The height h of the object after t seconds is given by the quadratic       Log On


   

Question 712033: an object is thrown upward from the top of a 144-foot building with a initial velocity of 128 feet per second. The height h of the object after t seconds is given by the quadratic equation h= -16t^(2)+128t+144. When will the object hit the ground?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
At +t+=+0+,
+h%280%29+=+-16%2A0%5E2%2B128%2A0%2B144+
+h%280%29+=+144+
which just means that the object is
+144+ ft above the ground
---------
When the object hits the ground, +h+=+0+
+h+=+-16%2At%5E2%2B128t%2B144+
+0+=+-16%2At%5E2%2B128t%2B144+
Divide both sides by +-16+
+t%5E2+-+8t+-+9+=+0+
+%28+t+-+9+%29%2A%28+t+%2B+1+%29+=+0+
+t+=+9+
The object hits the ground in 9 sec
The other solution is +t+=+-1+ sec
which is not possible.