试题:
比较a2-3a+1和a2+2a-5的大小.(作差法比大小)
整式的加减 2016-05-17

答案:

我来补答
a2-3a+1-(a2+2a-5),
=a2-3a+1-a2-2a+5,
=-5a+6,
(1)当-5a+6<0,即a>
6
5
时,
a2-3a+1<a2+2a-5;
(2)当-5a+6=0,即a=
6
5
时,
a2-3a+1=a2+2a-5;
(3)当-5a+6>0,即a<
6
5
时,
a2-3a+1>a2+2a-5.
 
 
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