设数列{an}为等比数列,数列{bn}满足bN=na1+(n-1)a2+…+2an-1+an ps:只需第三问!须详述!

问题描述:

设数列{an}为等比数列,数列{bn}满足bN=na1+(n-1)a2+…+2an-1+an ps:只需第三问!须详述!
设数列{an}为等比数列,数列{bn}满足bN=na1+(n-1)a2+…+2an-1+an,n属于正整数.已知b1=m,b2=3m/2,其中m不等于0
(1)求数列{an}的首项和公比;
(2)当m=1时,求bn;
(3)设Sn为数列{an}的前n项和,若对于任意的正整数n,都有Sn属于[1,3],求实数m的取值范围

a(n)=aq^(n-1),b(n) = na(1)+(n-1)a(2)+...+2a(n-1)+a(n),m=b(1)=a(1)=a,3m/2 = b(2) = 2a(1)+a(2) = 2m + a(2), a(2)=-m/2.q = a(2)/a(1)=-1/2a(n) = m*(-1/2)^(n-1).m=1时,a(n) = (-1/2)^(n-1).b(n) = n*1 + (n-1)...