56=(4x+6)(x-4)

Solution for 56=(4x+6)(x-4) equation:

56=(4x+6)(x-4)

We move all terms to the left:

56-((4x+6)(x-4))=0

We multiply parentheses ..

-((+4x^2-16x+6x-24))+56=0


We calculate terms in parentheses: -((+4x^2-16x+6x-24)), so:

(+4x^2-16x+6x-24)

We get rid of parentheses

4x^2-16x+6x-24

We add all the numbers together, and all the variables

4x^2-10x-24

Back to the equation:

-(4x^2-10x-24)


We get rid of parentheses

-4x^2+10x+24+56=0

We add all the numbers together, and all the variables

-4x^2+10x+80=0

a = -4; b = 10; c = +80;
Δ = b2-4ac
Δ = 102-4·(-4)·80
Δ = 1380
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:

$\sqrt{\Delta}=\sqrt{1380}=\sqrt{4*345}=\sqrt{4}*\sqrt{345}=2\sqrt{345}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(10)-2\sqrt{345}}{2*-4}=\frac{-10-2\sqrt{345}}{-8}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(10)+2\sqrt{345}}{2*-4}=\frac{-10+2\sqrt{345}}{-8}
$