以知N分之M=5分之3,求（M+N分之M）+（M—N分之M）—（M平方—N平方分之N平方）的值

m/n=3/5 则n/m=5/3m/(m+n)+m/(m-n)-[n^2/(m^2-n^2)]=[m(m-n)+m(m+n)-n^2]/(m^2-n^2)=(2m^2-n^2)/(m^2-n^2)=1+m^2/(m^2-n^2)=1+1/[1-(n/m)^2]=1+1/(1-25/9)=1+9/16=25/16