GRE数学：解难题，理脉络
<p> 1.<span word="GRE">GRE</span>数学题目之判断题</p><p> 例：<span word="The">The</span> <span word="symbol">symbol</span> ? <span word="represents">represents</span> <span word="one">one</span> <span word="of">of</span> <span word="the">the</span> <span word="four">four</span> <span word="operations">operations</span> <span word="of">of</span> <span word="addition">addition</span>, <span word="subtraction">subtraction</span>, <span word="multiplication">multiplication</span>, <span word="and">and</span> <span word="division">division</span>, <span word="and">and</span> 3 ? 1 = 3.</p><p> <span word="For">For</span> <span word="each">each</span> <span word="of">of</span> <span word="the">the</span> <span word="following">following</span> <span word="equations">equations</span>, <span word="indicate">indicate</span> <span word="whether">whether</span> <span word="the">the</span> <span word="equation">equation</span> <span word="must">must</span> <span word="be">be</span> <span word="true">true</span>, <span word="must">must</span> <span word="be">be</span> <span word="false">false</span>, <span word="or">or</span> <span word="could">could</span> <span word="be">be</span> <span word="either">either</span> <span word="true">true</span> <span word="or">or</span> <span word="false">false</span>.</p><p> <span word="Equation">Equation</span></p><p> <span word="Must">Must</span> <span word="Be">Be</span> <span word="True">True</span></p><p> <span word="Must">Must</span> <span word="Be">Be</span> <span word="False">False</span></p><p> <span word="Could">Could</span> <span word="Be">Be</span> <span word="True">True</span> <span word="or">or</span> <span word="False">False</span></p><p> 6 ? 2 = 3</p><p> 6 ? 2 = 4</p><p> 6 ? 2 = 12</p><p> <span word="Click">Click</span> <span word="on">on</span> <span word="your">your</span> <span word="choices">choices</span>.</p><p> <span word="Click">Click</span> <span word="on">on</span> <span word="the">the</span> <span word="answer">answer</span> <span word="box">box</span>， <span word="then">then</span> <span word="type">type</span> <span word="in">in</span> <span word="a">a</span> <span word="number">number</span>. <span word="Backspace">Backspace</span> <span word="to">to</span> <span word="erase">erase</span>.</p><p> <span word="GRE">GRE</span>数学中出现的非常规数学符号可以看成<span word="ETS">ETS</span>自己定义的一种运算。本题中，符号?代表的是加减乘除四种四则运算中的某一种，而且3?1=3，由这些已知条件可以推出?可以是，也可以不是。接下来就考察考生对于<span word="must">must</span> <span word="be">be</span> <span word="true">true</span>、<span word="could">could</span> <span word="be">be</span> <span word="true">true</span>这类逻辑判断语言的理解了。<span word="Must">Must</span> <span word="be">be</span> <span word="true">true</span>意为必然正确，在任何时候都不可违背;<span word="Could">Could</span> <span word="be">be</span> <span word="true">true</span>意为可以正确，即存在正确的可能。</p><p> 因此第一个等式6?2=3在?代表除时错误，但在?代表加、减、乘时正确，因此第一式应为<span word="could">could</span> <span word="be">be</span> <span word="true">true</span> <span word="or">or</span> <span word="false">false</span>有可能对也可能错;</p><p> 第二个等式6?2=4不论?代表什么都不正确，因此第二式应为<span word="must">must</span> <span word="be">be</span> <span word="false">false</span>一定错误;</p>
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