165=(x+4)(x+8)

Solution for 165=(x+4)(x+8) equation:

165=(x+4)(x+8)

We move all terms to the left:

165-((x+4)(x+8))=0

We multiply parentheses ..

-((+x^2+8x+4x+32))+165=0


We calculate terms in parentheses: -((+x^2+8x+4x+32)), so:

(+x^2+8x+4x+32)

We get rid of parentheses

x^2+8x+4x+32

We add all the numbers together, and all the variables

x^2+12x+32

Back to the equation:

-(x^2+12x+32)


We get rid of parentheses

-x^2-12x-32+165=0

We add all the numbers together, and all the variables

-1x^2-12x+133=0

a = -1; b = -12; c = +133;
Δ = b2-4ac
Δ = -122-4·(-1)·133
Δ = 676
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{676}=26$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-12)-26}{2*-1}=\frac{-14}{-2}
=+7
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-12)+26}{2*-1}=\frac{38}{-2}
=-19
$