(x+1)(x-5)=-8

Solution for (x+1)(x-5)=-8 equation:

(x+1)(x-5)=-8

We move all terms to the left:

(x+1)(x-5)-(-8)=0

We add all the numbers together, and all the variables

(x+1)(x-5)+8=0

We multiply parentheses ..

(+x^2-5x+x-5)+8=0

We get rid of parentheses

x^2-5x+x-5+8=0

We add all the numbers together, and all the variables

x^2-4x+3=0

a = 1; b = -4; c = +3;
Δ = b2-4ac
Δ = -42-4·1·3
Δ = 4
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{4}=2$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-4)-2}{2*1}=\frac{2}{2}
=1
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-4)+2}{2*1}=\frac{6}{2}
=3
$