450=x^2-40x

Solution for 450=x^2-40x equation:

450=x^2-40x

We move all terms to the left:

450-(x^2-40x)=0

We get rid of parentheses

-x^2+40x+450=0

We add all the numbers together, and all the variables

-1x^2+40x+450=0

a = -1; b = 40; c = +450;
Δ = b2-4ac
Δ = 402-4·(-1)·450
Δ = 3400
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:

$\sqrt{\Delta}=\sqrt{3400}=\sqrt{100*34}=\sqrt{100}*\sqrt{34}=10\sqrt{34}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(40)-10\sqrt{34}}{2*-1}=\frac{-40-10\sqrt{34}}{-2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(40)+10\sqrt{34}}{2*-1}=\frac{-40+10\sqrt{34}}{-2}
$