2x(3x+1)=15

Solution for 2x(3x+1)=15 equation:

2x(3x+1)=15

We move all terms to the left:

2x(3x+1)-(15)=0

We multiply parentheses

6x^2+2x-15=0

a = 6; b = 2; c = -15;
Δ = b2-4ac
Δ = 22-4·6·(-15)
Δ = 364
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{364}=\sqrt{4*91}=\sqrt{4}*\sqrt{91}=2\sqrt{91}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(2)-2\sqrt{91}}{2*6}=\frac{-2-2\sqrt{91}}{12}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(2)+2\sqrt{91}}{2*6}=\frac{-2+2\sqrt{91}}{12}
$