来自柴恩祥的问题
1/(a+b),1/(a+c),1/(b+c),是等差数列,求证,a^2,b^2,c^2成等差数列
1/(a+b),1/(a+c),1/(b+c),是等差数列,求证,a^2,b^2,c^2成等差数列
1回答
2020-03-06 13:03
1/(a+b),1/(a+c),1/(b+c),是等差数列,求证,a^2,b^2,c^2成等差数列
1/(a+b),1/(a+c),1/(b+c),是等差数列,求证,a^2,b^2,c^2成等差数列
1/(a+b)+1/(b+c)=2/(a+c)==>(b+c)(a+c)+(a+b)(a+c)=2(a+b)(b+c)
所以ba+bc+ac+c^2+a^2+ac+ab+bc=2ab+2ac+2b^2+2bc
整理得:a^2+c^2=2b^2,即a^2,b^2,c^2成等差数列