Question

已知A=

1

x-2

，B=

2

x2-4

，C=

x

x+2

．將它們組合成（A-B）÷C或A-B÷C的形式，請(qǐng)你從中任選一種進(jìn)行計(jì)算，先化簡(jiǎn)，再求值其中x=3．

Answer 1

選一：（A-B）÷C=(

1

x-2

-

2

x2-4

)÷

x

x+2

=

x

(x+2)(x-2)

×

x+2

x

=

1

x-2

．
當(dāng)x=3時(shí)，原式=

1

3-2

=1；
選二：A-B÷C=

1

x-2

-

2

x2-4

÷

x

x+2

=

1

x-2

-

2

(x+2)(x-2)

×

x+2

x

=

1

x-2

-

2

x(x-2)

=

x-2

x(x-2)

=

1

x

．
當(dāng)x=3時(shí)，原式=

1

3

．