(2x-4)(7x+8)=0

Solution for (2x-4)(7x+8)=0 equation:

(2x-4)(7x+8)=0

We multiply parentheses ..

(+14x^2+16x-28x-32)=0

We get rid of parentheses

14x^2+16x-28x-32=0

We add all the numbers together, and all the variables

14x^2-12x-32=0

a = 14; b = -12; c = -32;
Δ = b2-4ac
Δ = -122-4·14·(-32)
Δ = 1936
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1936}=44$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-12)-44}{2*14}=\frac{-32}{28}
=-1+1/7
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-12)+44}{2*14}=\frac{56}{28}
=2
$