(X-13)(x+18)=0

Solution for (X-13)(x+18)=0 equation:

(X-13)(X+18)=0

We multiply parentheses ..

(+X^2+18X-13X-234)=0

We get rid of parentheses

X^2+18X-13X-234=0

We add all the numbers together, and all the variables

X^2+5X-234=0

a = 1; b = 5; c = -234;
Δ = b2-4ac
Δ = 52-4·1·(-234)
Δ = 961
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{961}=31$
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(5)-31}{2*1}=\frac{-36}{2}
=-18
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(5)+31}{2*1}=\frac{26}{2}
=13
$