已知等差数列{an}为1,4,7,…,2011,等差数列{bn}为5,9,13,…,2013.试求{an}与{bn}的公
2个回答
an等差3,bn等差4,
公共项首项13,等差12组成新数列cn,
Scn=(13+13+12(n-1))×n/2
=(13+6n-6)×n
=(7+6n)xn
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