(X+4)(x-1)=5X+20

Solution for (X+4)(x-1)=5X+20 equation:

(X+4)(X-1)=5X+20

We move all terms to the left:

(X+4)(X-1)-(5X+20)=0

We get rid of parentheses

(X+4)(X-1)-5X-20=0

We multiply parentheses ..

(+X^2-1X+4X-4)-5X-20=0

We get rid of parentheses

X^2-1X+4X-5X-4-20=0

We add all the numbers together, and all the variables

X^2-2X-24=0

a = 1; b = -2; c = -24;
Δ = b2-4ac
Δ = -22-4·1·(-24)
Δ = 100
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{100}=10$
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-2)-10}{2*1}=\frac{-8}{2}
=-4
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-2)+10}{2*1}=\frac{12}{2}
=6
$