若1/x+1/y=2,則2x-xy+2y/3x+5y+3y=

就是利用的整體的代入法！！ 解：因為1/x+1/y=2 所以x+y=2xy （2x-xy+2y）/（3x+5xy+3y） =[2（x+y）-xy]/[3（x+y）+5xy] 將x+y=2xy代入上面的式子： =[4xy-xy]/[6xy+5xy] =3xy/11xy =3/11

X分之1加Y分之1＝2，則2X減XY加2Y除以3X加5XY加3Y＝？

1/x+1/y=2 (x+y)/xy=2 x+y=2xy (2x-xy+2y)/(3x+5xy+3y) =[2(x+y)-xy]/[3(x+y)+5xy] =(4xy-xy)/(6xy+5xy) =3xy/11xy =3/11

若1/x-1/y=2，則2x-3xy-2y/x-2xy-y的值是

1/x-1/y=2 (y-x)/(xy)=2 x-y=-2xy (2x-3xy-2y)/(x-2xy-y) =[2(x-y)-3xy]/[(x-y)-2xy] =[2(-2xy)-3xy]/(-2xy-2xy) =(-7xy)/(-4xy) =7/4

若1/x-1/y=2,求2x+xy-2y/3x-2xy-3y的值。

若1/x-1/y=2，則 2xy=x-y 2x+xy-2y/3x-2xy-3y=(2x+0.5x-0.5y-2y)/(3x+x-y-3y)=5/8=0.625

若1x+1y=2，則2x?xy+2y3x+5xy+3y=_____

由

1

x

+

1

y

=2，得x+y=2xy
則

2x?xy+2y

3x+5xy+3y

=

2(x+y)?xy

3(x+y)+5xy

=

2?2xy?xy

3?2xy+5xy

=

3xy

11xy

＝

3

11

．
故答案為

3

11

．