20^2=x^2-6x

Solution for 20^2=x^2-6x equation:

20^2=x^2-6x

We move all terms to the left:

20^2-(x^2-6x)=0

We add all the numbers together, and all the variables

-(x^2-6x)+400=0

We get rid of parentheses

-x^2+6x+400=0

We add all the numbers together, and all the variables

-1x^2+6x+400=0

a = -1; b = 6; c = +400;
Δ = b2-4ac
Δ = 62-4·(-1)·400
Δ = 1636
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:

$\sqrt{\Delta}=\sqrt{1636}=\sqrt{4*409}=\sqrt{4}*\sqrt{409}=2\sqrt{409}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(6)-2\sqrt{409}}{2*-1}=\frac{-6-2\sqrt{409}}{-2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(6)+2\sqrt{409}}{2*-1}=\frac{-6+2\sqrt{409}}{-2}
$