4m^2+3m*n-n^2/3m^2+4mn+n^2,если m/n=5/12

6-9n+6mn-4m

  3n2+n-2

(3(2-3n)-2m(2-3n))/((n+1)(3n-2))=((2-3n)(3-2m))/((n+1)(3n-2))=(2-3m)/(n+1)