若X\2=Y\3,则分式(7X²―y²)\(X²―2XY+3y²)的值是多少?

若X\2=Y\3,则分式(7X²―y²)\(X²―2XY+3y²)的值是多少?

令k=X\2=Y\3
则X=2k,Y=3k
所以(7X²―y²)\(X²―2XY+3y²)
=(28k²-9k²)/(4k²-12k²+27k²)
=19k²/(19k²)
=1

X\2=Y\3
x=2y/3
(7X²―y²)\(X²―2XY+3y²)
=(28y^2/9-y^2)/(4y^2/9-4y^2/3+3y^2)
=(19y^2/9) / (19y^2/9)
=1