Question

先化简，再求值

x+1

x2+1

÷

(x+1)3

x4-1

-

x-3

x+1

，其中x=

3

+1．

Answer 1

x+1

x2+1

÷

(x+1)3

x4-1

-

x-3

x+1

=

x+1

x2+1

•

(x2+1)(x+1)(x-1)

(x+1)3

-

x-3

x+1

=

x-1

x+1

-

x-3

x+1

=

2

x+1

；
当x=

3

+1时，
原式=

2

x+1

=

2

3 +1+1

=

2

3 +2

=2(2-

3

)=4-2

3

．