摘要：25．原式= =． 当x=时.原式=． 26先化简.再求值:. [关键词]分式求值 [答案]解:原式=------------2分 =------------------3分 =---------------4分 =---------------------5分 27当-------- 先化简.再求值: 其中 [关键词]分式求值 [答案]解:÷= 3分 =x+4············································································· 5分 当x =3时.原式=3+4 =7·································································································· 7分 28先化简:并任选一个你喜欢的数代入求值． [关键词]分式的化简求值 [答案]原式===．取0和1以外的任何数． 2917．先化简再计算:.其中=3.=2 [关键词]分解因式.分式运算 [答案]解:原式＝ ＝x+y-2x+y ＝-x+2y 因为 x＝3.y＝2 所以原式＝-3+4＝1 30化简: [关键词]约分与通分.分式运算 [答案]解:原式= =
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。计算：
．选择相应的步骤，将序号填在括号内：
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A．化除为乘； |
B．最后做减法； |
C．算乘方； |
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D．做乘法； |
E．确定积的符号 |
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解：原式= |
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的根号外面的因式移到根号内，则原式等于( )．
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