4(a-b)(b-c)-(a-c)^2=0 證2b=a+c

熱心網(wǎng)友

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