已知x/3=y/4,求7x²-y²/x²-2xy+3y²的值.

已知x/3=y/4,求7x²-y²/x²-2xy+3y²的值.
已知x/3=y/4,求7x²-y²/x²-2xy+3y²的值.

已知x/3=y/4,求7x²-y²/x²-2xy+3y²的值.
设x/3=y/4=k得：x=3k,y=4k
所以7x²-y²/x²-2xy+3y²=(7*9k^2-16k^2)/(9k^2-2*3*4k^2+3*16k^2)=47/33