Question

先化简，再求值

1

x+1

-

x+3

x2-1

÷

x2+4x+3

x2-2x+1

，其中x=

2

．

Answer 1

原式=

1

x+1

-

x+3

(x+1)(x-1)

•

(x-1)2

(x+1)(x+3)

=

1

x+1

-

x-1

(x+1)2

=

x+1-(x-1)

(x+1)2

=

2

(x+1)2

当x=

2

时，原式=

2

( 2 +1)2

=

2

2 2 +3

=6-4

2

．