已知x=根号5-2分之根号5-2,y=根号5+2分之根号5-2.求（1）x+y （2）xy （3）x+y分之x²+3xy+y²

x=(√5+2)/(√5-2) =(√5+2)²/[(√5-2)(√5+2)] =(9+4√5)/(5-2)=(9+4√5)/3 y=(√5-2)/(√5+2) =(√5-2)²/[(√5-2)(√5+2)] =(9-4√5)/(5-2)=(9-4√5)/3(1)x+y=(9+4√5)/3+(9-4√5)/3 =(9+9)/3 =...x， （√5-2）（√5+2)怎么是（5-2）x=(√5+2)/(√5-2) =(√5+2)²/[(√5-2)(√5+2)] =(9+4√5)/(5-4)=9+4√5 y=(√5-2)/(√5+2) =(√5-2)²/[(√5-2)(√5+2)] =(9-4√5)/(5-4)=9-4√5(1)x+y=(9+4√5)+(9-4√5) =9+9 =18(3)(x²+3xy+y²)/(x+y)=[(x+y)²+xy]/(x+y)=(18²+1)/18=325/18