(2x-1)(4x^2+2x+1)-2x(2x-1)(2x+1)=

(2x-1)(4x^2+2x+1)-2x(2x-1)(2x+1)

(2x-1)(4x^2+2x+1) = 8x^3+4x^2+2x-4x^2-2x-1 = 8x^3 -1

2x(2x-1)(2x+1) = 2x(4x^2-1) = 8x^3-2x

(2x-1)(4x^2+2x+1)-2x(2x-1)(2x+1) = 8x^3 -1 - ( 8x^3-2x) = 2x-1

Ответ:  2х-1