G(3b)=(3b)2-3b

Solution for G(3b)=(3b)2-3b equation:

(3G)=(3G)2-3G

We move all terms to the left:

(3G)-((3G)2-3G)=0

We add all the numbers together, and all the variables

-(+3G^2-3G)+3G=0

We get rid of parentheses

-3G^2+3G+3G=0

We add all the numbers together, and all the variables

-3G^2+6G=0

a = -3; b = 6; c = 0;
Δ = b2-4ac
Δ = 62-4·(-3)·0
Δ = 36
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$G_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$G_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{36}=6$
$G_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(6)-6}{2*-3}=\frac{-12}{-6}
=+2
$
$G_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(6)+6}{2*-3}=\frac{0}{-6}
=0
$