9x(x+13)=0

Solution for 9x(x+13)=0 equation:

9x(x+13)=0

We multiply parentheses

9x^2+117x=0

a = 9; b = 117; c = 0;
Δ = b2-4ac
Δ = 1172-4·9·0
Δ = 13689
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{13689}=117$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(117)-117}{2*9}=\frac{-234}{18}
=-13
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(117)+117}{2*9}=\frac{0}{18}
=0
$