问题标题:
已知数列{an},{bn}的前n项和分别为An,Bn,且A100=8,B100=251.记Cn=an•Bn+bn•An-an•bn(n∈N*),则数列{Cn}的前100项的和为______.
问题描述:
已知数列{an},{bn}的前n项和分别为An,Bn,且A100=8,B100=251.记Cn=an•Bn+bn•An-an•bn(n∈N*),则数列{Cn}的前100项的和为______.
汤彦回答:
Cn=an•Bn+bn•An-an•bn=(An-An-1)×Bn+(Bn-Bn-1)×An-(An-An-1)×(Bn-Bn-1)=An×Bn-An-1×Bn+Bn×An-Bn-1×An-(An×Bn-An-1×Bn-An×Bn-1+An-1×Bn-1]=An×Bn-An-1×Bn-1,∴Cn=An×Bn-An-1×Bn-1,Cn-1=...
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