GRE数学考生回忆（12）
<p> 47、问/<span word="a">a</span>2-<span word="b">b</span>2/是不是大于6? <span word="A">A</span>. /<span word="a">a</span>+<span word="b">b</span>/2 <span word="B">B</span>. /<span word="a">a</span>-<span word="b">b</span>/3</p><p> |<span word="a">a</span>2-<span word="b">b</span>2|=|| =|<span word="a">a</span>+<span word="b">b</span>||<span word="a">a</span>-<span word="b">b</span>| 条件1)+条件2) 0|<span word="a">a</span>+<span word="b">b</span>|2且 0|<span word="a">a</span>-<span word="b">b</span>|3 可以确定0|<span word="a">a</span>+<span word="b">b</span>||<span word="a">a</span>-<span word="b">b</span>| 6 选<span word="C">C</span></p><p> 48、有三个人<span word="x">x</span>,<span word="y">y</span>,<span word="z">z</span>决定平分房租，<span word="x">x</span>因为有<span word="pet">pet</span>，所以交了250刀的<span word="pet">pet</span> <span word="deposit">deposit</span>~所以<span word="x">x</span>一共花了525刀~问总的房租是多少~我思考了很久还是选了2753=825这个选项。 3 = 825刀</p><p> 49、说<span word="x">x</span>^2+<span word="ax">ax</span>+<span word="b">b</span>一共有两个正数根~问下面那个一定成立? 1.<span word="a">a</span>0 2.<span word="b">b</span>0 3.<span word="ab">ab</span>0</p><p> 由求根公式= -<span word="a">a</span>0 得<span word="a">a</span>0</p><p> 两个正数根 即 可知<span word="b">b</span>=<span word="x">x</span>1<span word="x">x</span>20 选1和3</p><p> </p>
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