GRE数学基本概念解析（例题）
<p> 因子，因数<span word="divisor">divisor</span>,<span word="factor">factor</span></p><p> 计算一个整数的因子数的方法：</p><p> 1、将该整数进行因数分解，写成质因数连乘的形式;</p><p> 2、把每个不同的质因数的指数分别加1，再把加1后的结果相乘，即可得到该整数所有不同的因子的数目。</p><p> 例10.5<span word="x">x</span>173有多少个不同的因子?</p><p> 例11.252有多少个不同的因子?</p><p> 倍数 <span word="multiple">multiple</span></p><p> <span word="The">The</span> <span word="least">least</span> <span word="common">common</span> <span word="multiple">multiple</span></p><p> 最小公倍数</p><p> <span word="The">The</span> <span word="greatest">greatest</span> <span word="common">common</span> <span word="factor">factor</span></p><p> 最大公约数</p><p> 整数的整除性质的判断：</p><p> 如果一个数各个数位数字之和是3的倍数，则这个数就是3的倍数;</p><p> 如果一个数末尾两位数是4的倍数，则这个数就是4的倍数;</p><p> 如果一个数即是偶数又是3的倍数，则这个数就是6的倍数。</p><p> 0可以被除了0以外的其他所有整数整除</p><p> 例题.<span word="If">If</span> <span word="x">x</span> <span word="is">is</span> <span word="an">an</span> <span word="odd">odd</span> <span word="integer">integer</span>, <span word="then">then</span> <span word="x">x</span>2-1<span word="must">must</span> <span word="be">be</span></p><p> <span word="A">A</span>. <span word="a">a</span> <span word="prime">prime</span> <span word="number">number</span></p><p> <span word="B">B</span>. <span word="an">an</span> <span word="odd">odd</span> <span word="integer">integer</span></p><p> <span word="C">C</span>. <span word="divisible">divisible</span> <span word="by">by</span> 8</p><p> <span word="D">D</span>. <span word="a">a</span> <span word="multiple">multiple</span> <span word="of">of</span> 2<span word="x">x</span></p><p> <span word="E">E</span>. <span word="a">a</span> <span word="positive">positive</span> <span word="integer">integer</span></p><p> <span word="x">x</span>=2<span word="k">k</span>+1 <span word="or">or</span> 2<span word="k">k</span>-1</p>
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