180=(x+1)(3x)+90

Solution for 180=(x+1)(3x)+90 equation:

180=(x+1)(3x)+90

We move all terms to the left:

180-((x+1)(3x)+90)=0


We calculate terms in parentheses: -((x+1)3x+90), so:

(x+1)3x+90

We multiply parentheses

3x^2+3x+90

Back to the equation:

-(3x^2+3x+90)


We get rid of parentheses

-3x^2-3x-90+180=0

We add all the numbers together, and all the variables

-3x^2-3x+90=0

a = -3; b = -3; c = +90;
Δ = b2-4ac
Δ = -32-4·(-3)·90
Δ = 1089
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1089}=33$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-3)-33}{2*-3}=\frac{-30}{-6}
=+5
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-3)+33}{2*-3}=\frac{36}{-6}
=-6
$