计算:m-21/m^2-9 - 3/3-m另:_数学解答

计算:m-21/m^2-9 - 3/3-m
另:

人气：408 ℃　时间：2020-06-27 04:57:34

解答

(m-21)/(m^2-9)-3/(3-m)
=(m-21)/(m^2-9)+3(m+3)/(m^2-9)
=(m-21+3m+9)/(m^2-9)
=(4m-12)/(m^2-9)
=4(m-3)/(m+3)(m-3)
=4/(m+3)