4x(2x+3)=56

Solution for 4x(2x+3)=56 equation:

4x(2x+3)=56

We move all terms to the left:

4x(2x+3)-(56)=0

We multiply parentheses

8x^2+12x-56=0

a = 8; b = 12; c = -56;
Δ = b2-4ac
Δ = 122-4·8·(-56)
Δ = 1936
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1936}=44$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(12)-44}{2*8}=\frac{-56}{16}
=-3+1/2
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(12)+44}{2*8}=\frac{32}{16}
=2
$