0=-5x^2-20x+7

Solution for 0=-5x^2-20x+7 equation:

0=-5x^2-20x+7

We move all terms to the left:

0-(-5x^2-20x+7)=0

We add all the numbers together, and all the variables

-(-5x^2-20x+7)=0

We get rid of parentheses

5x^2+20x-7=0

a = 5; b = 20; c = -7;
Δ = b2-4ac
Δ = 202-4·5·(-7)
Δ = 540
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:

$\sqrt{\Delta}=\sqrt{540}=\sqrt{36*15}=\sqrt{36}*\sqrt{15}=6\sqrt{15}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(20)-6\sqrt{15}}{2*5}=\frac{-20-6\sqrt{15}}{10}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(20)+6\sqrt{15}}{2*5}=\frac{-20+6\sqrt{15}}{10}
$