(x+-7)(2x+-8)=0

Solution for (x+-7)(2x+-8)=0 equation:

(x+-7)(2x+-8)=0

We add all the numbers together, and all the variables

(x-7)(2x-8)=0

We multiply parentheses ..

(+2x^2-8x-14x+56)=0

We get rid of parentheses

2x^2-8x-14x+56=0

We add all the numbers together, and all the variables

2x^2-22x+56=0

a = 2; b = -22; c = +56;
Δ = b2-4ac
Δ = -222-4·2·56
Δ = 36
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{36}=6$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-22)-6}{2*2}=\frac{16}{4}
=4
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-22)+6}{2*2}=\frac{28}{4}
=7
$