x(3x+3)=85

Solution for x(3x+3)=85 equation:

x(3x+3)=85

We move all terms to the left:

x(3x+3)-(85)=0

We multiply parentheses

3x^2+3x-85=0

a = 3; b = 3; c = -85;
Δ = b2-4ac
Δ = 32-4·3·(-85)
Δ = 1029
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:

$\sqrt{\Delta}=\sqrt{1029}=\sqrt{49*21}=\sqrt{49}*\sqrt{21}=7\sqrt{21}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(3)-7\sqrt{21}}{2*3}=\frac{-3-7\sqrt{21}}{6}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(3)+7\sqrt{21}}{2*3}=\frac{-3+7\sqrt{21}}{6}
$