X^2+4x-255=0

Solution for X^2+4x-255=0 equation:

X^2+4X-255=0

a = 1; b = 4; c = -255;
Δ = b2-4ac
Δ = 42-4·1·(-255)
Δ = 1036
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:

$\sqrt{\Delta}=\sqrt{1036}=\sqrt{4*259}=\sqrt{4}*\sqrt{259}=2\sqrt{259}$
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(4)-2\sqrt{259}}{2*1}=\frac{-4-2\sqrt{259}}{2}
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(4)+2\sqrt{259}}{2*1}=\frac{-4+2\sqrt{259}}{2}
$