630=-40x+x^2

Solution for 630=-40x+x^2 equation:

630=-40x+x^2

We move all terms to the left:

630-(-40x+x^2)=0

We get rid of parentheses

-x^2+40x+630=0

We add all the numbers together, and all the variables

-1x^2+40x+630=0

a = -1; b = 40; c = +630;
Δ = b2-4ac
Δ = 402-4·(-1)·630
Δ = 4120
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:

$\sqrt{\Delta}=\sqrt{4120}=\sqrt{4*1030}=\sqrt{4}*\sqrt{1030}=2\sqrt{1030}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(40)-2\sqrt{1030}}{2*-1}=\frac{-40-2\sqrt{1030}}{-2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(40)+2\sqrt{1030}}{2*-1}=\frac{-40+2\sqrt{1030}}{-2}
$