题目

x=(a+3)(a-5)与y=(a+2)(a-4)的大小关系是(  ) A.x>y                                                          B.x=y C.x<y                                                          D.不能确定 答案:C [解析] ∵x-y=a2+3a-5a-15-a2-2a+4a+8 =-7<0,∴x<y.
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