(7x-7)(4x+8)=0

Solution for (7x-7)(4x+8)=0 equation:

(7x-7)(4x+8)=0

We multiply parentheses ..

(+28x^2+56x-28x-56)=0

We get rid of parentheses

28x^2+56x-28x-56=0

We add all the numbers together, and all the variables

28x^2+28x-56=0

a = 28; b = 28; c = -56;
Δ = b2-4ac
Δ = 282-4·28·(-56)
Δ = 7056
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{7056}=84$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(28)-84}{2*28}=\frac{-112}{56}
=-2
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(28)+84}{2*28}=\frac{56}{56}
=1
$