先化简，再求值：1a+1+1a(a+1)+a2?aa2?2a+1，其中a＝23+1
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∵a＝
=
-1，
∴a-1=
-1-1＜0，
+
+
，
=
+
+
，
=
+
-
，
=
+
-a，
=
| 2 | ||
|
| 3 |
∴a-1=
| 3 |
| 1 |
| a+1 |
| 1 |
| a(a+1) |
| a2?a | ||
|
=
| 1 |
| a+1 |
| 1 |
| a(a+1) |
| a(a?1) | ||
|
=
| 1 |
| a+1 |
| 1 |
| a(a+1) |
| a(a?1) |
| a?1 |
=
| a |
| a(a+1) |
| 1 |
| a(a+1) |
=
