(-x+7)(-x-11)=0

Solution for (-x+7)(-x-11)=0 equation:

(-x+7)(-x-11)=0

We add all the numbers together, and all the variables

(-1x+7)(-1x-11)=0

We multiply parentheses ..

(+x^2+11x-7x-77)=0

We get rid of parentheses

x^2+11x-7x-77=0

We add all the numbers together, and all the variables

x^2+4x-77=0

a = 1; b = 4; c = -77;
Δ = b2-4ac
Δ = 42-4·1·(-77)
Δ = 324
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{324}=18$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(4)-18}{2*1}=\frac{-22}{2}
=-11
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(4)+18}{2*1}=\frac{14}{2}
=7
$