-4.9t^2+6t+800=0

Solution for -4.9t^2+6t+800=0 equation:

-4.9t^2+6t+800=0

a = -4.9; b = 6; c = +800;
Δ = b2-4ac
Δ = 62-4·(-4.9)·800
Δ = 15716
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{15716}=\sqrt{4*3929}=\sqrt{4}*\sqrt{3929}=2\sqrt{3929}$
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(6)-2\sqrt{3929}}{2*-4.9}=\frac{-6-2\sqrt{3929}}{-9.8}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(6)+2\sqrt{3929}}{2*-4.9}=\frac{-6+2\sqrt{3929}}{-9.8}
$