(c+9)(c+6)=0

Solution for (c+9)(c+6)=0 equation:

(c+9)(c+6)=0

We multiply parentheses ..

(+c^2+6c+9c+54)=0

We get rid of parentheses

c^2+6c+9c+54=0

We add all the numbers together, and all the variables

c^2+15c+54=0

a = 1; b = 15; c = +54;
Δ = b2-4ac
Δ = 152-4·1·54
Δ = 9
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$c_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$c_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{9}=3$
$c_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(15)-3}{2*1}=\frac{-18}{2}
=-9
$
$c_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(15)+3}{2*1}=\frac{-12}{2}
=-6
$