共50条信息
已知数列\(\{a_{n}\}\)是以\(a\)为首项,\(b\)为公比的等比数列,数列\(\{b_{n}\}\)满足\(b_{n}=1+a_{1}+a_{2}+…+a_{n}(n=1,2,…)\),数列\(\{c_{n}\}\)满足\(c_{n}=2+b_{1}+b_{2}+…+b_{n}(n=1,2,…)\),若\(\{c_{n}\}\)为等比数列,则\(a+b=\)
在各项均为正数的等比数列\(\{a_{n}\}\)中,\(a_{6}=3\),则\(a_{4}+a_{8}\)
一直角三角形三边长成等比数列,则( )
数列\(\left\{ {{a}_{n}} \right\}\)是各项为正数的等比数列,且\({{a}_{4}}=2\),已知函数\(f(x)={\log }_{ \frac{1}{2}}x \),则\(f\left( a_{1}^{3} \right)+f\left( a_{2}^{3} \right)+\cdot \cdot \cdot +f\left( a_{7}^{3} \right)=\)( )
已知等比数列\(\{\)\(a_{n}\)\(\}\)满足\(a\)\({\,\!}_{1}=3\),\(a\)\({\,\!}_{1}+\)\(a\)\({\,\!}_{3}+\)\(a\)\({\,\!}_{5}=21\),则\(a\)\({\,\!}_{3}+\)\(a\)\({\,\!}_{5}+\)\(a\)\({\,\!}_{7}=(\) \()\)
已知数列\(\{a_{n}\}\)为等比数列,\(a_{4}+a_{7}=2\),\(a_{⋅}a_{6}=-8\),则\(a_{1}+a_{10}\)的值为\((\) \()\)
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