(-x-1)(x+2)=0

Solution for (-x-1)(x+2)=0 equation:

(-x-1)(x+2)=0

We add all the numbers together, and all the variables

(-1x-1)(x+2)=0

We multiply parentheses ..

(-1x^2-2x-1x-2)=0

We get rid of parentheses

-1x^2-2x-1x-2=0

We add all the numbers together, and all the variables

-1x^2-3x-2=0

a = -1; b = -3; c = -2;
Δ = b2-4ac
Δ = -32-4·(-1)·(-2)
Δ = 1
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1}=1$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-3)-1}{2*-1}=\frac{2}{-2}
=-1
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-3)+1}{2*-1}=\frac{4}{-2}
=-2
$