(2x-1)(16x^4+8a^3+4x^2++2x+1)=

(2x-1)(16x^4+8a^3+4x^2++2x+1)=

(2x-1)(16x^4+8x^3+4x^2+2x+1)
=32x^5-16x^4+16x^4-8x^3+8x^3-4x^2+4x^2-2x+2x-1
=32x^5-1