;2的2m-4次方乘16乘8m次方+（-4的m次方）乘8的m次方
=2^(2m-4)*2^4*2^3m-4^m*8^m
=2^(2m-4)*2^(4+3m)-2^5m
=2^5m-2^5m
=0^啥意思，谢谢^表示次方x^2表示x的2次方