4.905t^2-6.465t+0.65=0

Solution for 4.905t^2-6.465t+0.65=0 equation:

4.905t^2-6.465t+0.65=0

a = 4.905; b = -6.465; c = +0.65;
Δ = b2-4ac
Δ = -6.4652-4·4.905·0.65
Δ = 29.043225
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{-(-6.465)-\sqrt{29.043225}}{2*4.905}=\frac{6.465-\sqrt{29.043225}}{9.81}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-6.465)+\sqrt{29.043225}}{2*4.905}=\frac{6.465+\sqrt{29.043225}}{9.81}
$