-4.9t2-1.55t+5=0

Solution for -4.9t2-1.55t+5=0 equation:

-4.9t^2-1.55t+5=0

a = -4.9; b = -1.55; c = +5;
Δ = b2-4ac
Δ = -1.552-4·(-4.9)·5
Δ = 100.4025
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{-(-1.55)-\sqrt{100.4025}}{2*-4.9}=\frac{1.55-\sqrt{100.4025}}{-9.8}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-1.55)+\sqrt{100.4025}}{2*-4.9}=\frac{1.55+\sqrt{100.4025}}{-9.8}
$