h represents the height of the ball at a given time, symbolised as t.
Thus, we just need to find when h = 0 so that we find when it hits the ground.
0 = -4.9t² + 19.6t + 58.8
0 = 4.9t² - 19.6t - 58.8
0 = 49t² - 196t - 588
0 = t² - 4t - 12
0 = (t - 6)(t + 2)
So, t = 6 or -2, but t ≠ -2, since time cannot be negative in this instance.
Hence, at 6 seconds, the ball will strike the ground.
