A ball is thrown into the air with an upward velocity of 48ft/s. It's height h in feet after t seconds is given by the function h=-16t^+48t+8. In how many seconds will the ball hit the ground?

Question

A ball is thrown into the air with an upward velocity of 48ft/s. It's height h in feet after t seconds is given by the function h=-16t^+48t+8. In how many seconds will the ball hit the ground? 
I got 1.5 seconds put when I plug it back into the equation, I get it wrong. Thanks for helping!!

Steve · Answer

-16t^2 + 48t + 8 = 0 first factor out a -8, and you have 2t^2 - 6t - 1 = 0 1.5 is not a root of that quadratic.