Question

where does 2x' come?
|x^2-x'^2| = |x-x'||2x'+(x-x')|

Answer 1

if a = x and b = x', this is how it comes........
( a^2-b^2)
=(a-b)(a+b)
=(a-b)(2a-a+b)
=(a-b)(2a+(b-a))