图望采纳
(1)x+1/x=3x^2+1/x^2 +2 =9x^2+1/x^2 =7x^2/(x^4+x^2+1)=1/( x^2 +1 +1/x^2)=1/(7+1)=1/8(2)1/x-1/y=2y-x =2xyx-y =-2xy(4x+5xy-4y)/(x-3xy-y)=[ 4(x-y)+5xy] /[ (x-y) -3xy]=(-8+5).( -2 -3)=3/5