Question

当a=

2

1- 3

时，求

a2-1

a-1

-

a2+2a+1

a2+a

-

1

a

的值．

Answer 1

∵a=

2

1- 3

=-1- 

3

，
∴

a2+2a+1

=-a-1

a2 -1

a-1

-

a2 +2a+1

a2 +a

-

1

a

=a+1+

1

a

-

1

a

=a+1=-

3

．