A girl stands on the edge of her dorm roof and throws a ball into the air. The ball's height above the ground after t seconds is given by h=−16t^2+64t+80. When will the ball hit the ground?
+37170 Just set the equation given to = 0 and solve for 't' (when the equation = 0 the ball is on the ground)
0 = -16t^2 + 64t +80 (make things simpler...divide thru by 8)
0=-2t^2+8t+10 quadratic formula yields 5 sec (or -1 which is invalid for a TIME)
