8a的立方bm的次方÷28a的n次方b方=2/7b方a方8a的立方bm的次方÷28a的n次方b方=8/28a^(3-n)b^(m-2)=2/7a^2b^23-n=2m-2=2m-2-(3-n)=0m-5+n=0m+n=5
