3x^2+9x+15=9

Solution for 3x^2+9x+15=9 equation:

3x^2+9x+15=9

We move all terms to the left:

3x^2+9x+15-(9)=0

We add all the numbers together, and all the variables

3x^2+9x+6=0

a = 3; b = 9; c = +6;
Δ = b2-4ac
Δ = 92-4·3·6
Δ = 9
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{9}=3$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(9)-3}{2*3}=\frac{-12}{6}
=-2
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(9)+3}{2*3}=\frac{-6}{6}
=-1
$