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

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

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

We multiply parentheses ..

(+2x^2+14x-4x-28)=0

We get rid of parentheses

2x^2+14x-4x-28=0

We add all the numbers together, and all the variables

2x^2+10x-28=0

a = 2; b = 10; c = -28;
Δ = b2-4ac
Δ = 102-4·2·(-28)
Δ = 324
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{324}=18$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(10)-18}{2*2}=\frac{-28}{4}
=-7
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(10)+18}{2*2}=\frac{8}{4}
=2
$