(x+4)(2x-1)=56

Solution for (x+4)(2x-1)=56 equation:

(x+4)(2x-1)=56

We move all terms to the left:

(x+4)(2x-1)-(56)=0

We multiply parentheses ..

(+2x^2-1x+8x-4)-56=0

We get rid of parentheses

2x^2-1x+8x-4-56=0

We add all the numbers together, and all the variables

2x^2+7x-60=0

a = 2; b = 7; c = -60;
Δ = b2-4ac
Δ = 72-4·2·(-60)
Δ = 529
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{529}=23$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(7)-23}{2*2}=\frac{-30}{4}
=-7+1/2
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(7)+23}{2*2}=\frac{16}{4}
=4
$