[(2^3-1)(3^3-1)...100^3-1)]/[(2^3+1)(3^3+1)...(100^3+1)]=?

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[(2^3-1)(3^3-1)...100^3-1)]/[(2^3+1)(3^3+1)...(100^3+1)]=?

[(2^3-1)(3^3-1)...100^3-1)]/[(2^3+1)(3^3+1)...(100^3+1)]=?
[(2^3-1)(3^3-1)...100^3-1)]/[(2^3+1)(3^3+1)...(100^3+1)]=?

[(2^3-1)(3^3-1)...100^3-1)]/[(2^3+1)(3^3+1)...(100^3+1)]=?
100很大,你可以设通项为(n^3-1)/(n^3+1),原式为n从2到100通项的乘积 ∏(n^3-1)/(n^3+1) =∏(n-1)[n(n+1)+1]/{(n+1)[(n-1)n+1]} =∏[(n-1)/(n+1)]*∏{[n(n+1)+1]/[(n-1)n+1]} ={2/[n(n+1)]}{[n(n+1)+1]/(1*2+1)} =(2/3){[n(n+1)+1]/[n(n+1)]} [n(n+1)+1]/[n(n+1)]当n很大时,趋于1 ∴(2/3){[n(n+1)+1]/[n(n+1)]}趋于2/3