72=(x+2)(x+8)

Solution for 72=(x+2)(x+8) equation:

72=(x+2)(x+8)

We move all terms to the left:

72-((x+2)(x+8))=0

We multiply parentheses ..

-((+x^2+8x+2x+16))+72=0


We calculate terms in parentheses: -((+x^2+8x+2x+16)), so:

(+x^2+8x+2x+16)

We get rid of parentheses

x^2+8x+2x+16

We add all the numbers together, and all the variables

x^2+10x+16

Back to the equation:

-(x^2+10x+16)


We get rid of parentheses

-x^2-10x-16+72=0

We add all the numbers together, and all the variables

-1x^2-10x+56=0

a = -1; b = -10; c = +56;
Δ = b2-4ac
Δ = -102-4·(-1)·56
Δ = 324
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{324}=18$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-10)-18}{2*-1}=\frac{-8}{-2}
=+4
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-10)+18}{2*-1}=\frac{28}{-2}
=-14
$