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

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

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

We multiply parentheses ..

(+28x^2+28x-32x-32)=0

We get rid of parentheses

28x^2+28x-32x-32=0

We add all the numbers together, and all the variables

28x^2-4x-32=0

a = 28; b = -4; c = -32;
Δ = b2-4ac
Δ = -42-4·28·(-32)
Δ = 3600
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{3600}=60$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-4)-60}{2*28}=\frac{-56}{56}
=-1
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-4)+60}{2*28}=\frac{64}{56}
=1+1/7
$