—个有趣的定值命题及其引伸

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众所周知,在直角坐标平面内,若点M((?,?))为有限点集{A<sub>1</sub>,A<sub>2</sub>,…,A<sub>n</sub>}的重心,A<sub>i</sub>(i=1,2,…,n)的坐标为(x<sub>i</sub>,y<sub>i</sub>),则有 (?)=1/n sum from i=1 to n(x<sub>i<
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