(x+1)(-4x+5)=0

Solution for (x+1)(-4x+5)=0 equation:

(x+1)(-4x+5)=0

We multiply parentheses ..

(-4x^2+5x-4x+5)=0

We get rid of parentheses

-4x^2+5x-4x+5=0

We add all the numbers together, and all the variables

-4x^2+x+5=0

a = -4; b = 1; c = +5;
Δ = b2-4ac
Δ = 12-4·(-4)·5
Δ = 81
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{81}=9$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(1)-9}{2*-4}=\frac{-10}{-8}
=1+1/4
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(1)+9}{2*-4}=\frac{8}{-8}
=-1
$