(X-8)(x-11)=70

Solution for (X-8)(x-11)=70 equation:

(X-8)(X-11)=70

We move all terms to the left:

(X-8)(X-11)-(70)=0

We multiply parentheses ..

(+X^2-11X-8X+88)-70=0

We get rid of parentheses

X^2-11X-8X+88-70=0

We add all the numbers together, and all the variables

X^2-19X+18=0

a = 1; b = -19; c = +18;
Δ = b2-4ac
Δ = -192-4·1·18
Δ = 289
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{289}=17$
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-19)-17}{2*1}=\frac{2}{2}
=1
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-19)+17}{2*1}=\frac{36}{2}
=18
$