Question

已知

1

b

-

1

a

=1，試求

2a+3ab-2b

a-2ab-b

的值．

Answer 1

分析：首先根據(jù)

1

b

-

1

a

=1，推出a-b=ab，然后對(duì)分式進(jìn)行化簡(jiǎn)，最后把a(bǔ)-b=ab代入求值即可．

解答：解：由

1

b

-

1

a

=1得，a-b=ab．
∴

2a+3ab-2b

a-2ab-b

=

2(a-b)+3ab

(a-b)-2ab

=

2ab+3ab

ab-2ab

=

5ab

-ab

=-5．

點(diǎn)評(píng)：本題主要考查分式的化簡(jiǎn)求值，關(guān)鍵在于求出a-b=ab．