4x(x+3)=55

Solution for 4x(x+3)=55 equation:

4x(x+3)=55

We move all terms to the left:

4x(x+3)-(55)=0

We multiply parentheses

4x^2+12x-55=0

a = 4; b = 12; c = -55;
Δ = b2-4ac
Δ = 122-4·4·(-55)
Δ = 1024
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1024}=32$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(12)-32}{2*4}=\frac{-44}{8}
=-5+1/2
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(12)+32}{2*4}=\frac{20}{8}
=2+1/2
$