Robert drops a ball from his balcony. The height of the ball is modeled by the function $h(x) = -2t^2 +t +11$. How many many seconds will it take for his ball to reach the ground?
The correct answer is $t = 2.85$ seconds. However, I tried using the quadratic formula or deriving this equation to solve it but I'm not getting the right answer. Help!
Best Answer
You want to set the height equal to zero, since that's when the ball hits the ground. Knowing that, now you can apply the quadratic formula to $-2t^2 +t+11 = 0$ to get $$t = \frac{-1 \pm \sqrt{89}}{-4} $$ which gives you the answer. I'm pretty sure the 2.85 is just wrong