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

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

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

We multiply parentheses ..

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

We get rid of parentheses

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

We add all the numbers together, and all the variables

28x^2-28=0

a = 28; b = 0; c = -28;
Δ = b2-4ac
Δ = 02-4·28·(-28)
Δ = 3136
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{3136}=56$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-56}{2*28}=\frac{-56}{56}
=-1
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+56}{2*28}=\frac{56}{56}
=1
$