(2x-2)(21x+2)=0

Solution for (2x-2)(21x+2)=0 equation:

(2x-2)(21x+2)=0

We multiply parentheses ..

(+42x^2+4x-42x-4)=0

We get rid of parentheses

42x^2+4x-42x-4=0

We add all the numbers together, and all the variables

42x^2-38x-4=0

a = 42; b = -38; c = -4;
Δ = b2-4ac
Δ = -382-4·42·(-4)
Δ = 2116
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{2116}=46$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-38)-46}{2*42}=\frac{-8}{84}
=-2/21
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-38)+46}{2*42}=\frac{84}{84}
=1
$