设数列{an}是以2为首项,1为公差的等差数列, {bn}是以1为首项,2为公比的等比数列,则ab1+ab2+...+ab10=?ab1中b1为项数,跟n一样拉THX答案是2057... T T
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![设数列{an}是以2为首项,1为公差的等差数列, {bn}是以1为首项,2为公比的等比数列,则ab1+ab2+...+ab10=?ab1中b1为项数,跟n一样拉THX答案是2057... T T](/uploads/image/z/14579194-58-4.jpg?t=%E8%AE%BE%E6%95%B0%E5%88%97%7Ban%7D%E6%98%AF%E4%BB%A52%E4%B8%BA%E9%A6%96%E9%A1%B9%2C1%E4%B8%BA%E5%85%AC%E5%B7%AE%E7%9A%84%E7%AD%89%E5%B7%AE%E6%95%B0%E5%88%97%2C+%7Bbn%7D%E6%98%AF%E4%BB%A51%E4%B8%BA%E9%A6%96%E9%A1%B9%2C2%E4%B8%BA%E5%85%AC%E6%AF%94%E7%9A%84%E7%AD%89%E6%AF%94%E6%95%B0%E5%88%97%2C%E5%88%99ab1%2Bab2%2B...%2Bab10%3D%3Fab1%E4%B8%ADb1%E4%B8%BA%E9%A1%B9%E6%95%B0%2C%E8%B7%9Fn%E4%B8%80%E6%A0%B7%E6%8B%89THX%E7%AD%94%E6%A1%88%E6%98%AF2057...++T+T)
设数列{an}是以2为首项,1为公差的等差数列, {bn}是以1为首项,2为公比的等比数列,则ab1+ab2+...+ab10=?ab1中b1为项数,跟n一样拉THX答案是2057... T T
设数列{an}是以2为首项,1为公差的等差数列, {bn}是以1为首项,2为公比的等比数列,则ab1+ab2+...+ab10=?
ab1中b1为项数,跟n一样拉THX
答案是2057... T T
设数列{an}是以2为首项,1为公差的等差数列, {bn}是以1为首项,2为公比的等比数列,则ab1+ab2+...+ab10=?ab1中b1为项数,跟n一样拉THX答案是2057... T T
a(n)= 2+(n-1)*1 =n +1
b(n) =1 *2^(n-1) =2^(n-1)
依题意有:
M(n) =a(1) +a(2) +a(4) + .a(2^(n-1))
=(1 +1) +(2+1) +..(2^(n-1) +1) (共n项)
= (1 +2 +.+2^(n-1)) +(1+1+.+1) (共有n个1)
=(2^n -1) +n
=2^n + n -1
M[(10)=2^10 +10-1= 1024+9=1033
答案是:ab1+ab2+...+ab10=1033
An = n + 1; Bn = 2^(n-1)
A(Bn)项 = Bn + 1
A(B1) + A(B2)... + A(B10) = B1 + B2 + B3 ... + B10 + 10
B1 + B2 + B3... + B10 = 2^10-1
所以,前十项 = 2^10 -1 + 10 = 1033
答案是2036 你们都做错了