3x^2-12x^2-15x=0

Solution for 3x^2-12x^2-15x=0 equation:

3x^2-12x^2-15x=0

We add all the numbers together, and all the variables

-9x^2-15x=0

a = -9; b = -15; c = 0;
Δ = b2-4ac
Δ = -152-4·(-9)·0
Δ = 225
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{225}=15$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-15)-15}{2*-9}=\frac{0}{-18}
=0
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-15)+15}{2*-9}=\frac{30}{-18}
=-1+2/3
$