an,(bn)^2,a(n+1)成等差數(shù)列,(bn)^2,a(n+1),(b(n+1))^2成等比數(shù)列,證:(bn)為等差數(shù)列
an,(bn)^2,a(n+1)成等差數(shù)列,(bn)^2,a(n+1),(b(n+1))^2成等比數(shù)列,證:(bn)為等差數(shù)列
數(shù)學(xué)人氣:527 ℃時(shí)間:2020-08-01 19:40:10
優(yōu)質(zhì)解答
由題an,(bn)^2,a(n+1)成等差數(shù)列2(bn)^2=an+a(n+1)--①由(bn)^2,a(n+1),(b(n+1))^2成等比數(shù)列(a(n+1))^2=[bnb(n+1)]^2∴a(n+1)=bnb(n+1)在①中有2(bn)^2=bn(b(n-1)+b(n+1))即2bn=b(n-1)+b(n+1)故{bn}為等差數(shù)列...
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