(b-9)(b+36)=0

Solution for (b-9)(b+36)=0 equation:

(b-9)(b+36)=0

We multiply parentheses ..

(+b^2+36b-9b-324)=0

We get rid of parentheses

b^2+36b-9b-324=0

We add all the numbers together, and all the variables

b^2+27b-324=0

a = 1; b = 27; c = -324;
Δ = b2-4ac
Δ = 272-4·1·(-324)
Δ = 2025
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{2025}=45$
$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(27)-45}{2*1}=\frac{-72}{2}
=-36
$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(27)+45}{2*1}=\frac{18}{2}
=9
$