49=34.4t-4.905t^2

Solution for 49=34.4t-4.905t^2 equation:

49=34.4t-4.905t^2

We move all terms to the left:

49-(34.4t-4.905t^2)=0

We get rid of parentheses

4.905t^2-34.4t+49=0

a = 4.905; b = -34.4; c = +49;
Δ = b2-4ac
Δ = -34.42-4·4.905·49
Δ = 221.98
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-34.4)-\sqrt{221.98}}{2*4.905}=\frac{34.4-\sqrt{221.98}}{9.81}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-34.4)+\sqrt{221.98}}{2*4.905}=\frac{34.4+\sqrt{221.98}}{9.81}
$