y'=5(2x+1)^4*2*(4-x)³+(2x+1)^5*3(4-x)²*(-1)
=10(2x+1)^4*(4-x)³-3(2x+1)^5(4-x)²
=(2x+1)^4(4-x)²(40-10x-6x-3)