题目内容
若x=30，那么| x |
| x-3 |
| x+6 |
| x2-3x |
| 1 |
| x |
分析：首先通分，然后进行同分母的分式的加减计算，约分，最后把x的值代入即可求解．
解答：解：
-
+
=
-
+
=
-
+
=
=
=
=
，
当x=30时，原式=
=
．
故答案是：
．
| x |
| x-3 |
| x+6 |
| x2-3x |
| 1 |
| x |
=
| x |
| x-3 |
| x+6 |
| x(x-3) |
| 1 |
| x |
=
| x2 |
| x(x-3) |
| x+6 |
| x(x-3) |
| x-3 |
| x(x-3) |
=
| x2-x-6+x-3 |
| x(x-3) |
=
| x2-9 |
| x(x-3) |
=
| (x+3)(x-3) |
| x(x-3) |
=
| x+3 |
| x |
当x=30时，原式=
| 30+3 |
| 30 |
| 11 |
| 10 |
故答案是：
| 11 |
| 10 |
点评：本题考查了分式的化简求值，关键是正确进行分式的化简．
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