已知a=11/19x+20 b=11/19x+19 - 知识问答

已知a=11/19x+20 b=11/19x+19 c=11/19x+21求a²+b²+c²

2个回答

a=11/19x+20 b=11/19x+19 c=11/19x+21
a-b=1 b-c=-2 c-a=1
a²+b²+c²-ab-bc-ac
=(1/2)(2a²+2b²+2c²-2ab-2bc-2ca)
=(1/2)[(a²-2ab+b²)+(b²-2bc+c²)+(c²-2ca+a²)]
=(1/2)[(a-b)²+(b-c)²+(c-a)²]
=(1/2)[1²+(-2)²+1²]
=(1/2)×6
=3

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