4.905t^2-6.88t+0.65=0

Solution for 4.905t^2-6.88t+0.65=0 equation:

4.905t^2-6.88t+0.65=0

a = 4.905; b = -6.88; c = +0.65;
Δ = b2-4ac
Δ = -6.882-4·4.905·0.65
Δ = 34.5814
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{-(-6.88)-\sqrt{34.5814}}{2*4.905}=\frac{6.88-\sqrt{34.5814}}{9.81}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-6.88)+\sqrt{34.5814}}{2*4.905}=\frac{6.88+\sqrt{34.5814}}{9.81}
$