18=2x+3(x)2

Solution for 18=2x+3(x)2 equation:

18=2x+3(x)2

We move all terms to the left:

18-(2x+3(x)2)=0

We add all the numbers together, and all the variables

-(+2x+3x^2)+18=0

We get rid of parentheses

-3x^2-2x+18=0

a = -3; b = -2; c = +18;
Δ = b2-4ac
Δ = -22-4·(-3)·18
Δ = 220
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:

$\sqrt{\Delta}=\sqrt{220}=\sqrt{4*55}=\sqrt{4}*\sqrt{55}=2\sqrt{55}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-2)-2\sqrt{55}}{2*-3}=\frac{2-2\sqrt{55}}{-6}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-2)+2\sqrt{55}}{2*-3}=\frac{2+2\sqrt{55}}{-6}
$