20*15=20x*20x-x^2

Solution for 20*15=20x*20x-x^2 equation:

20*15=20x*20x-x^2

We move all terms to the left:

20*15-(20x*20x-x^2)=0

We add all the numbers together, and all the variables

-(20x*20x-x^2)+300=0

We get rid of parentheses

x^2-20x*20x+300=0

Wy multiply elements

x^2-400x^2+300=0

We add all the numbers together, and all the variables

-399x^2+300=0

a = -399; b = 0; c = +300;
Δ = b2-4ac
Δ = 02-4·(-399)·300
Δ = 478800
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:

$\sqrt{\Delta}=\sqrt{478800}=\sqrt{3600*133}=\sqrt{3600}*\sqrt{133}=60\sqrt{133}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-60\sqrt{133}}{2*-399}=\frac{0-60\sqrt{133}}{-798}
=-\frac{60\sqrt{133}}{-798}
=-\frac{10\sqrt{133}}{-133}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+60\sqrt{133}}{2*-399}=\frac{0+60\sqrt{133}}{-798}
=\frac{60\sqrt{133}}{-798}
=\frac{10\sqrt{133}}{-133}
$