2x(3x+1)-28=0

Solution for 2x(3x+1)-28=0 equation:

2x(3x+1)-28=0

We multiply parentheses

6x^2+2x-28=0

a = 6; b = 2; c = -28;
Δ = b2-4ac
Δ = 22-4·6·(-28)
Δ = 676
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{676}=26$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(2)-26}{2*6}=\frac{-28}{12}
=-2+1/3
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(2)+26}{2*6}=\frac{24}{12}
=2
$