Question

若

x-y

x+y

=2，則

x-y

x+y

-

2(x+y)

3(x-y)

=

 

．

Answer 1

考點(diǎn)：分式的化簡求值

專題：

分析：根據(jù)已知條件得到

x+y

x-y

=

1

2

，所以把

x-y

x+y

=2、

x+y

x-y

=

1

2

代入所求的代數(shù)式進(jìn)行求值即可．

解答：解：∵

x-y

x+y

=2，
∴

x+y

x-y

=

1

2

，
∴

x-y

x+y

-

2(x+y)

3(x-y)

=2-

2

3

×

x+y

x-y

=2-

2

3

×

1

2

=

5

3

．
故答案是：

5

3

．

點(diǎn)評：本題考查了分式的化簡求值．解答此題的關(guān)鍵是把分式化到最簡，然后代值計算．