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

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

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

We move all terms to the left:

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

We multiply parentheses ..

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

We get rid of parentheses

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

We add all the numbers together, and all the variables

2x^2+5x-54=0

a = 2; b = 5; c = -54;
Δ = b2-4ac
Δ = 52-4·2·(-54)
Δ = 457
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(5)-\sqrt{457}}{2*2}=\frac{-5-\sqrt{457}}{4}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(5)+\sqrt{457}}{2*2}=\frac{-5+\sqrt{457}}{4}
$