165=(x+10)(x+6)

Solution for 165=(x+10)(x+6) equation:

165=(x+10)(x+6)

We move all terms to the left:

165-((x+10)(x+6))=0

We multiply parentheses ..

-((+x^2+6x+10x+60))+165=0


We calculate terms in parentheses: -((+x^2+6x+10x+60)), so:

(+x^2+6x+10x+60)

We get rid of parentheses

x^2+6x+10x+60

We add all the numbers together, and all the variables

x^2+16x+60

Back to the equation:

-(x^2+16x+60)


We get rid of parentheses

-x^2-16x-60+165=0

We add all the numbers together, and all the variables

-1x^2-16x+105=0

a = -1; b = -16; c = +105;
Δ = b2-4ac
Δ = -162-4·(-1)·105
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{-(-16)-26}{2*-1}=\frac{-10}{-2}
=+5
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-16)+26}{2*-1}=\frac{42}{-2}
=-21
$