(x+1)(13-4x)=0

Solution for (x+1)(13-4x)=0 equation:

(x+1)(13-4x)=0

We add all the numbers together, and all the variables

(x+1)(-4x+13)=0

We multiply parentheses ..

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

We get rid of parentheses

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

We add all the numbers together, and all the variables

-4x^2+9x+13=0

a = -4; b = 9; c = +13;
Δ = b2-4ac
Δ = 92-4·(-4)·13
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*-4}=\frac{-26}{-8}
=3+1/4
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(9)+17}{2*-4}=\frac{8}{-8}
=-1
$