X(x-4)=4

Solution for X(x-4)=4 equation:

X(X-4)=4

We move all terms to the left:

X(X-4)-(4)=0

We multiply parentheses

X^2-4X-4=0

a = 1; b = -4; c = -4;
Δ = b2-4ac
Δ = -42-4·1·(-4)
Δ = 32
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:

$\sqrt{\Delta}=\sqrt{32}=\sqrt{16*2}=\sqrt{16}*\sqrt{2}=4\sqrt{2}$
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-4)-4\sqrt{2}}{2*1}=\frac{4-4\sqrt{2}}{2}
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-4)+4\sqrt{2}}{2*1}=\frac{4+4\sqrt{2}}{2}
$