Please, use " ^ " to indicate exponentiation: f(t) = −5t^2 + 20t + 60.
When the object hits the ground, f(t) = 0 = −5t^2 + 20t + 60
We must solve this quadratic equation for t. Start by dividing all 4 terms by -5:
t^2 - 4t - 12 = 0. Factoring, we get (t-6)(t+2)=0. Thus, t=6. Omit t=-2.
How many seconds does it take the object to hit the ground? 6 seconds.
