已知a-b=b-c=3/5,a^2+b^2=1,则ab+bc+ca的值等于?
已知a-b=b-c=3/5,a^2+b^2=1,则ab+bc+ca的值等于?
数学人气:662 ℃时间:2019-10-19 15:47:02
优质解答
a-b=3/5 b-c=3/5 相加 a-c=6/5 (a-b)²+(b-c)²+(c-a)²=9/25+9/25+36/25 a²-2ab+b²+b²-2bc+c²+c²-2ca+c²=54/25 2(a²+b²+c²)-2(ab+bc+ca)=54/25 2*1-2(ab...你看错题了吧
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