平均数为(x1+x2)/2S²={[x1-(x1+x2)/2]²+[x2-(x1+x2)/2]²}/2=2即：(x1-x2)²/4+(x2-x1)²/4=4(x1-x2)²/2=4(x1-x2)²=8x1-x2=±2√2如果不懂,请Hi我,