-4.9*x^2-20*x=-50

Solution for -4.9*x^2-20*x=-50 equation:

-4.9x^2-20x=-50

We move all terms to the left:

-4.9x^2-20x-(-50)=0

We add all the numbers together, and all the variables

-4.9x^2-20x+50=0

a = -4.9; b = -20; c = +50;
Δ = b2-4ac
Δ = -202-4·(-4.9)·50
Δ = 1380
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:

$\sqrt{\Delta}=\sqrt{1380}=\sqrt{4*345}=\sqrt{4}*\sqrt{345}=2\sqrt{345}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-20)-2\sqrt{345}}{2*-4.9}=\frac{20-2\sqrt{345}}{-9.8}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-20)+2\sqrt{345}}{2*-4.9}=\frac{20+2\sqrt{345}}{-9.8}
$