Question

計算

1

x+1

+

1

x2-1

+

1

1-x

的結(jié)果為（　�。�

• A．

  1

  x2-1

• B．

  2x+1

  x2-1

• C．

  -1

  x-1

• D．

  -1

  x2-1

Answer 1

分析：首先通分，然后利用同分母的分式相加減的運(yùn)算法則求解即可求得答案．

解答：解：

1

x+1

+

1

x2-1

+

1

1-x

=

x-1

(x+1)(x-1)

+

1

(x+1)(x-1)

-

x+1

(x+1)(x-1)

=

x-1+1-(x+1)

(x+1)(x-1)

=-

1

(x+1)(x-1)

=

-1

x2-1

．
故選D．

點(diǎn)評：此題考查了分式的加減運(yùn)算法則．此題比較簡單，注意準(zhǔn)確通分是解此題的關(guān)鍵，注意運(yùn)算結(jié)果需化為最簡．