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

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

(X+8)(X-1)=8

We move all terms to the left:

(X+8)(X-1)-(8)=0

We multiply parentheses ..

(+X^2-1X+8X-8)-8=0

We get rid of parentheses

X^2-1X+8X-8-8=0

We add all the numbers together, and all the variables

X^2+7X-16=0

a = 1; b = 7; c = -16;
Δ = b2-4ac
Δ = 72-4·1·(-16)
Δ = 113
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(7)-\sqrt{113}}{2*1}=\frac{-7-\sqrt{113}}{2}
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(7)+\sqrt{113}}{2*1}=\frac{-7+\sqrt{113}}{2}
$