(2y+1)^2×(2y+1)^3+(2y+1)^4【-(2y+1)】
=(2y+1)^5 - (2y+1)^5
=0错了吧，看我算的(2y+1)^2×(2y+1)^3+(2y+1)^4【-(2y+1)】=- [（2y+1）^(2+3+4+1)]= - (2y+1)^10对不对？你错了！注意前面没有负号，而【-(2y+1)】只对(2y+1)^4起作用！