题目内容
计算
-
+
．
| 1 |
| 2x2+3x-1 |
| 2 |
| 2x2+3x+1 |
| 1 |
| 2x2+3x+3 |
分析：设2x2+3x=y，原式可变形为
-
+
，再通分化简计算即可．
| 1 |
| y-1 |
| 2 |
| y+1 |
| 1 |
| y+3 |
解答：解：设2x2+3x=y，则
原式=
-
+
=
=
=
．
原式=
| 1 |
| y-1 |
| 2 |
| y+1 |
| 1 |
| y+3 |
=
| (y+1)(y+3)-2(y-1)(y+3)+(y-1)(y+1) |
| (y-1)(y+1)(y+3) |
=
| 8 |
| (y-1)(y+1)(y+3) |
=
| 8 |
| (2x2+3x-1)(2x2+3x+1)(2x2+3x+3) |
点评：此题主要考查了分式的加减运算，关键是掌握换元法的应用．
练习册系列答案
相关题目