4/(x的四次方)-2/(x的平方)=3,(2/x^2)^2-2/x^2-3=0,(2/x^2+1)(2/x^2-3)=0,∴2/x^2=3.y的四次方+y的平方=3,(y^2)^2+y^2-3=0,y^2>=0,∴y^2=(-1+√13)/2,∴4/x^4+y^4=9+(14-2√13)/4=(25-√13)/2....
(2/x^2+1)(2/x^2-3)=0,怎么能成立?
(2/x^2)^2-2/x^2-3=0,∴2/x^2=(1+√13)/2.y的四次方+y的平方=3,(y^2)^2+y^2-3=0,y^2>=0,∴y^2=(-1+√13)/2,∴4/x^4+y^4=[(1+√13)/2]^2+[(-1+√13)/2]^2=7.