720=(2x-6)(x-6)

Solution for 720=(2x-6)(x-6) equation:

720=(2x-6)(x-6)

We move all terms to the left:

720-((2x-6)(x-6))=0

We multiply parentheses ..

-((+2x^2-12x-6x+36))+720=0


We calculate terms in parentheses: -((+2x^2-12x-6x+36)), so:

(+2x^2-12x-6x+36)

We get rid of parentheses

2x^2-12x-6x+36

We add all the numbers together, and all the variables

2x^2-18x+36

Back to the equation:

-(2x^2-18x+36)


We get rid of parentheses

-2x^2+18x-36+720=0

We add all the numbers together, and all the variables

-2x^2+18x+684=0

a = -2; b = 18; c = +684;
Δ = b2-4ac
Δ = 182-4·(-2)·684
Δ = 5796
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{5796}=\sqrt{36*161}=\sqrt{36}*\sqrt{161}=6\sqrt{161}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(18)-6\sqrt{161}}{2*-2}=\frac{-18-6\sqrt{161}}{-4}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(18)+6\sqrt{161}}{2*-2}=\frac{-18+6\sqrt{161}}{-4}
$