Y=3x2+9x

Solution for Y=3x2+9x equation:

=3Y^2+9Y

We move all terms to the left:

-(3Y^2+9Y)=0

We get rid of parentheses

-3Y^2-9Y=0

a = -3; b = -9; c = 0;
Δ = b2-4ac
Δ = -92-4·(-3)·0
Δ = 81
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$Y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$Y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{81}=9$
$Y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-9)-9}{2*-3}=\frac{0}{-6}
=0
$
$Y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-9)+9}{2*-3}=\frac{18}{-6}
=-3
$