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

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

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

We multiply parentheses ..

(+8x^2+56x-4x-28)=0

We get rid of parentheses

8x^2+56x-4x-28=0

We add all the numbers together, and all the variables

8x^2+52x-28=0

a = 8; b = 52; c = -28;
Δ = b2-4ac
Δ = 522-4·8·(-28)
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{-(52)-60}{2*8}=\frac{-112}{16}
=-7
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(52)+60}{2*8}=\frac{8}{16}
=1/2
$