A girl is throwing a ball.
If I have an equation $h= -4.9*t^2+20t+1.2$, where $t$ is number of second after the girl has thrown the ball, and $h$ is the height above ground. I want to find out when will the ball hit the ground. My solution is set $-4.9*t^2+20t+1.2=0$, and then I get $t=4.1$ seconds. Is it correct?
An it is wrong to say that we solve $-4.9*t^2+20t+1.2=4.1$ and then solve for $t$. Am I right?