计算:a2-(a+1)(a-1)的结果是( )A.1B.-1C.2a2+1D.2a2-1
题型:单选题难度:一般来源:不详
答案
a2-(a+1)(a-1), =a2-(a2-1), =a2-a2+1, =1. 故选A. |
举一反三
计算下列各题 (1)(+1)(-1)+(-2)2(2)-. |
下列各式:a-b=b-a,(a-b)2=(b-a)2,x2+y2=(x+y)(x+y),-x2+y2=(-x+y)(-x-y),-a2+2ab-b2=-(a+b)2,a2b2+4ab-4=(ab-2)2,其中变形正确的有( )个. |
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