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问题: 初2因式分解

4(a-b)(b-c)-(a-c)^2=0 证2b=a+c

解答:

4(a-b)(b-c)-(a-c)^2 = 4(a-b)(b-c)-[(a-b)+(b-c)]^2
= 4(a-b)(b-c)-[(a-b)^+(b-c)^2 + 2(a-b)(b-c)]
= -[(a-b)^+(b-c)^2 - 2(a-b)(b-c)]
= -[(a-b)-(b-c)]^2 = -(a+c-2b)^2
= 0
==> 2b = a+c