若(m-2n)/(2m+n)=3,则[3(m-2n)/(2m+n)-(m-2n)/[2(2m+n)] - {9(m-2n)/[4(2m+n)]}的值是?

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若(m-2n)/(2m+n)=3,则[3(m-2n)/(2m+n)-(m-2n)/[2(2m+n)] - {9(m-2n)/[4(2m+n)]}的值是?
若(m-2n)/(2m+n)=3,则[3(m-2n)/(2m+n)-(m-2n)/[2(2m+n)] - {9(m-2n)/[4(2m+n)]}的值是?

若(m-2n)/(2m+n)=3,则[3(m-2n)/(2m+n)-(m-2n)/[2(2m+n)] - {9(m-2n)/[4(2m+n)]}的值是?
(m-2n)/(2m+n)=3
m-2n=6m+3n
5m+5n=0
m=-n
[3(m-2n)/(2m+n)-(m-2n)/[2(2m+n)] - {9(m-2n)/[4(2m+n)]}
=[3(-n-2n)/(-2n+n)-(-n-2n)/2(-2n+n)]-[9(-n-2n)/4(-2n+n)]
=(9-3/2)-27/4
=3/4

原式=(3)*3-(1/2)*3-(9/4)*3=3/4

3/4