-4.9x^2+8x+80=0

Solution for -4.9x^2+8x+80=0 equation:

-4.9x^2+8x+80=0

a = -4.9; b = 8; c = +80;
Δ = b2-4ac
Δ = 82-4·(-4.9)·80
Δ = 1632
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{1632}=\sqrt{16*102}=\sqrt{16}*\sqrt{102}=4\sqrt{102}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(8)-4\sqrt{102}}{2*-4.9}=\frac{-8-4\sqrt{102}}{-9.8}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(8)+4\sqrt{102}}{2*-4.9}=\frac{-8+4\sqrt{102}}{-9.8}
$