4x=4-x^2

Solution for 4x=4-x^2 equation:

4x=4-x^2

We move all terms to the left:

4x-(4-x^2)=0

We get rid of 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}
$