Question

1

a+1

-

a+3

a2-1

×

a2-2a+1

(a+1)(a-3)

，其中a²+2a-1=0．

Answer 1

1

a+1

-

a+3

a2-1

×

a2-2a+1

(a+1)(a+3)

=

1

a+1

-

a+3

(a+1)(a-1)

×

(a-1)2

(a+1)(a+3)

=

1

a+1

-

a-1

(a+1)2

=

a+1-a+1

(a+1)2

=

2

(a+1)2

=

2

a2+2a+1

；
当a²+2a-1=0即a²+2a=1时，原式=

2

1+1

=1．