3x(x+6)=30

Solution for 3x(x+6)=30 equation:

3x(x+6)=30

We move all terms to the left:

3x(x+6)-(30)=0

We multiply parentheses

3x^2+18x-30=0

a = 3; b = 18; c = -30;
Δ = b2-4ac
Δ = 182-4·3·(-30)
Δ = 684
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:

$\sqrt{\Delta}=\sqrt{684}=\sqrt{36*19}=\sqrt{36}*\sqrt{19}=6\sqrt{19}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(18)-6\sqrt{19}}{2*3}=\frac{-18-6\sqrt{19}}{6}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(18)+6\sqrt{19}}{2*3}=\frac{-18+6\sqrt{19}}{6}
$