计算：+-九年级数学

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• 问题探索：（1）已知一个正分数（m＞n＞0），如果分子、分母同时增加1，分数的值是增大还是减小？请证明你的结论；（2）若正分数（m＞n＞0）中分子和分母同时增加2，3…k（整数k＞0），情况如何-八年
• 已知：x=，y=，求代数式的值。-九年级数学
• 先阅读下列文字，再解答下列问题：数学课本中有这样一段叙述：“要比较a与b的大小，可先求出a与b的差，再看这个差是正数、负数还是零。”由此可见，要判断两个代数式值的大小，只-九年级数学
• 请你阅读下列计算过程，再回答所提出的问题。=x-3-3（x+1）C=-2x-6D①上述计算过程中，从哪一步开始出现错误__________；②从B到C是否正确？_________，若不正确，错误的原因
• 若，则的值为（）。-九年级数学
• 计算的结果是[]A.B.C.1D.-1-九年级数学
• 下列计算正确的是[]A．B．C．D．-九年级数学
• 如果（a+1）2+（2b+3）2+|c-1|=0，那么的值是多少？-七年级数学
• 已知，则的值等于[]A.6B.-3C.D.-八年级数学
• 已知两个分式：，，其x≠±2中，则A与B的关系是[]A.相等B.互为倒数C.互为相反数D.A大于B-八年级数学
• 化简：x-+2=（）。-八年级数学
• 化简：-九年级数学
• 计算：=（）。-九年级数学
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• — How cold the weather is! I wonder how the crops survive under such heavy snow? — Don't worry.
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• China is a country _____ 56 different nationalities, among which Han _____ the majority of its popul
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• After World War II, many of the buildings in the city _____. [ ]A. lied in ruinsB. lied in ruin C. l
• 甲、乙两人两次同时在同一粮店购买粮食（假设两次购买粮食的单价不相同），甲每次购买粮食100kg，乙每次购粮用去100元。（1）设第一、第二次购粮单价分别为x元/kg和y元/kg，用含-八年级数学
• 计算：=（）。-九年级数学
• 已知，则（）。-八年级数学