(-1-5x)(8+x)=0

Solution for (-1-5x)(8+x)=0 equation:

(-1-5x)(8+x)=0

We add all the numbers together, and all the variables

(-5x-1)(x+8)=0

We multiply parentheses ..

(-5x^2-40x-1x-8)=0

We get rid of parentheses

-5x^2-40x-1x-8=0

We add all the numbers together, and all the variables

-5x^2-41x-8=0

a = -5; b = -41; c = -8;
Δ = b2-4ac
Δ = -412-4·(-5)·(-8)
Δ = 1521
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1521}=39$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-41)-39}{2*-5}=\frac{2}{-10}
=-1/5
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-41)+39}{2*-5}=\frac{80}{-10}
=-8
$