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

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

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

We multiply parentheses ..

(+7x^2-14x+2x-4)=0

We get rid of parentheses

7x^2-14x+2x-4=0

We add all the numbers together, and all the variables

7x^2-12x-4=0

a = 7; b = -12; c = -4;
Δ = b2-4ac
Δ = -122-4·7·(-4)
Δ = 256
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{256}=16$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-12)-16}{2*7}=\frac{-4}{14}
=-2/7
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-12)+16}{2*7}=\frac{28}{14}
=2
$