数列求和.已知an=(0.5)^n,设bn/an=(2n+5)/((2n+1)(2n+3)),求bn的前n项和.
来源:学生作业帮 编辑:作业帮 分类:数学作业 时间:2024/05/26 00:19:08
数列求和.已知an=(0.5)^n,设bn/an=(2n+5)/((2n+1)(2n+3)),求bn的前n项和.
n/an = (2n+5)/[(2n+1)(2n+3)]
= 2/(2n+1) - 1/(2n+3)
bn =[2/(2n+1) - 1/(2n+3)] (0.5)^n
Sn = b1+b2+..+bn
= [( 1/3 -1/10)+ (1/10-1/28)+(1/28-1/72)+.( 2/(2n+1)(0.5)^n - 1/[2^n(2n+3)]) ]
= 1/3 - 1/[2^n(2n+3)]
= 2/(2n+1) - 1/(2n+3)
bn =[2/(2n+1) - 1/(2n+3)] (0.5)^n
Sn = b1+b2+..+bn
= [( 1/3 -1/10)+ (1/10-1/28)+(1/28-1/72)+.( 2/(2n+1)(0.5)^n - 1/[2^n(2n+3)]) ]
= 1/3 - 1/[2^n(2n+3)]
数列求和.已知an=(0.5)^n,设bn/an=(2n+5)/((2n+1)(2n+3)),求bn的前n项和.
an=2*3^n-1 若数列bn满足bn=an+(-1)^n*ln(an),求数列bn前n项和Sn
已知数列(2^n-1 an)的前n项和sn=9-6n.设bn=1/3(1-n)乘以an
已知数列{an}中an=-2n+11,如果bn=|an|(n属于N)求数列{bn}前n项和
an=3*2^(n-1),设bn=n/an求数列bn的前n项和Tn
在数列an中a1=2,a(n+1)下标=4an-3n+1 1设bn=an-n求证bn是等比数列 2求数列an的前n项和s
已知数列{an}的前n项和Sn=3×(3/2)^(n-1)-1,数列{bn}满足bn=a(n+1)/log3/2(an+
已知数列{an}的前n项和为Sn=n+n,求1)数列{an}的通项公式2)若bn=(1/2)^an+n,求{bn}的前n
【数列求和】已知Cn=an*bn=2^n*(2n)求{cn}的前n项和Tn
已知数列(An)满足A1=1 An+1=3An 数列(Bn)前n项和Sn=n*n+2n+1
已知数列{an}的通项公式an=2n-21,前n项和sn.如果bn=|an|(n∈N),求数列{bn}的前n项和Tn.
已知数列{an}的通项公式an=-2n+11,前n项和sn.如果bn=|an|(n∈N),求数列{bn}的前n项和Tn.