数列{an}中,an=32,Sn=63,(1)若数列{an}公差为11的等差数列,求a1(2)若数列{an}为以a1=1为首的等比数列,求数列{an^2}的前m项和Sm
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数列{an}中,an=32,Sn=63,(1)若数列{an}公差为11的等差数列,求a1(2)若数列{an}为以a1=1为首的等比数列,求数列{an^2}的前m项和Sm
数列{an}中,an=32,Sn=63,(1)若数列{an}公差为11的等差数列,求a1
(2)若数列{an}为以a1=1为首的等比数列,求数列{an^2}的前m项和Sm
数列{an}中,an=32,Sn=63,(1)若数列{an}公差为11的等差数列,求a1(2)若数列{an}为以a1=1为首的等比数列,求数列{an^2}的前m项和Sm
(1)n(a1+an)/2=Sn=63
a1+(n-1)*11=an=32
解方程组得 a1=10 n=3
(2)a1*q^(n-1)=32
a1(1-q^n)/(1-q)=63
解方程组得q=2 n=6
所以{an^2}是首项为1^2=1,公比为2^2=4的等比数列
Sm=1*(1-4^n)/(1-4)=(4^n-1)/3
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