x(x-5)=644

Solution for x(x-5)=644 equation:

x(x-5)=644

We move all terms to the left:

x(x-5)-(644)=0

We multiply parentheses

x^2-5x-644=0

a = 1; b = -5; c = -644;
Δ = b2-4ac
Δ = -52-4·1·(-644)
Δ = 2601
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{2601}=51$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-5)-51}{2*1}=\frac{-46}{2}
=-23
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-5)+51}{2*1}=\frac{56}{2}
=28
$