-56=-2(-4-5a)+6a(a+8)

Solution for -56=-2(-4-5a)+6a(a+8) equation:

-56=-2(-4-5a)+6a(a+8)

We move all terms to the left:

-56-(-2(-4-5a)+6a(a+8))=0

We add all the numbers together, and all the variables

-(-2(-5a-4)+6a(a+8))-56=0


We calculate terms in parentheses: -(-2(-5a-4)+6a(a+8)), so:

-2(-5a-4)+6a(a+8)

We multiply parentheses

6a^2+10a+48a+8

We add all the numbers together, and all the variables

6a^2+58a+8

Back to the equation:

-(6a^2+58a+8)


We get rid of parentheses

-6a^2-58a-8-56=0

We add all the numbers together, and all the variables

-6a^2-58a-64=0

a = -6; b = -58; c = -64;
Δ = b2-4ac
Δ = -582-4·(-6)·(-64)
Δ = 1828
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{1828}=\sqrt{4*457}=\sqrt{4}*\sqrt{457}=2\sqrt{457}$
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-58)-2\sqrt{457}}{2*-6}=\frac{58-2\sqrt{457}}{-12}
$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-58)+2\sqrt{457}}{2*-6}=\frac{58+2\sqrt{457}}{-12}
$