(x+4)*(x-13)=0

Solution for (x+4)*(x-13)=0 equation:

(x+4)(x-13)=0

We multiply parentheses ..

(+x^2-13x+4x-52)=0

We get rid of parentheses

x^2-13x+4x-52=0

We add all the numbers together, and all the variables

x^2-9x-52=0

a = 1; b = -9; c = -52;
Δ = b2-4ac
Δ = -92-4·1·(-52)
Δ = 289
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{289}=17$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-9)-17}{2*1}=\frac{-8}{2}
=-4
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-9)+17}{2*1}=\frac{26}{2}
=13
$