（1）8^(m+n)=2^[3(m+n)]=[2^(3m)]×[2^(3n)]=(2^m)³×(2^n)³=a³b³（2）2^(m+n)+2^(3m+2n)=(2^m)×(2^n)+(2^m)³+(2^n)²=ab+a³+b²