Question

代数式2m=3n,则m/(m+n)-m/(m-n)-2n^2/(m^2-n^2)=

Answer 1

m/(m+n)-m/(m-n)-2n^2/(m^2-n^2)

= m(m-n)/(m^2-n^2)-m(m+n)/(m^2-n^2)-2n^2/(m^2-n^2)

= (m^2-mn-m^2-mn-2n^2)/(m^2-n^2)

= 2n(m+n)/(n+m)(n-m)

= 2n/(n-m)

2m=3n m=1.5n

2n/(n-m)=-4