数列{an}中,a1=2,a(n+1)=a(n)+2n.(1)求{an}的通项公式(2)若a(n)+3n-2=2/b(n),求数列{bn}的前n项和S数列{an}中,a1=2,a(n+1)=a(n)+2n.(1)求{an}的通项公式 (2)若a(n)+3n-2=2/b(n),求数列{bn}的前n项和S(n)
来源:学生作业帮助网 编辑:作业帮 时间:2024/07/05 05:27:54
![数列{an}中,a1=2,a(n+1)=a(n)+2n.(1)求{an}的通项公式(2)若a(n)+3n-2=2/b(n),求数列{bn}的前n项和S数列{an}中,a1=2,a(n+1)=a(n)+2n.(1)求{an}的通项公式 (2)若a(n)+3n-2=2/b(n),求数列{bn}的前n项和S(n)](/uploads/image/z/3951604-28-4.jpg?t=%E6%95%B0%E5%88%97%7Ban%7D%E4%B8%AD%2Ca1%3D2%2Ca%28n%2B1%29%3Da%28n%29%2B2n.%EF%BC%881%EF%BC%89%E6%B1%82%7Ban%7D%E7%9A%84%E9%80%9A%E9%A1%B9%E5%85%AC%E5%BC%8F%EF%BC%882%EF%BC%89%E8%8B%A5a%28n%29%2B3n-2%3D2%2Fb%28n%29%2C%E6%B1%82%E6%95%B0%E5%88%97%7Bbn%7D%E7%9A%84%E5%89%8Dn%E9%A1%B9%E5%92%8CS%E6%95%B0%E5%88%97%7Ban%7D%E4%B8%AD%2Ca1%3D2%2Ca%28n%2B1%29%3Da%28n%29%2B2n.%EF%BC%881%EF%BC%89%E6%B1%82%7Ban%7D%E7%9A%84%E9%80%9A%E9%A1%B9%E5%85%AC%E5%BC%8F+%EF%BC%882%EF%BC%89%E8%8B%A5a%28n%29%2B3n-2%3D2%2Fb%28n%29%2C%E6%B1%82%E6%95%B0%E5%88%97%7Bbn%7D%E7%9A%84%E5%89%8Dn%E9%A1%B9%E5%92%8CS%28n%29)
数列{an}中,a1=2,a(n+1)=a(n)+2n.(1)求{an}的通项公式(2)若a(n)+3n-2=2/b(n),求数列{bn}的前n项和S数列{an}中,a1=2,a(n+1)=a(n)+2n.(1)求{an}的通项公式 (2)若a(n)+3n-2=2/b(n),求数列{bn}的前n项和S(n)
数列{an}中,a1=2,a(n+1)=a(n)+2n.(1)求{an}的通项公式(2)若a(n)+3n-2=2/b(n),求数列{bn}的前n项和S
数列{an}中,a1=2,a(n+1)=a(n)+2n.(1)求{an}的通项公式 (2)若a(n)+3n-2=2/b(n),求数列{bn}的前n项和S(n)
数列{an}中,a1=2,a(n+1)=a(n)+2n.(1)求{an}的通项公式(2)若a(n)+3n-2=2/b(n),求数列{bn}的前n项和S数列{an}中,a1=2,a(n+1)=a(n)+2n.(1)求{an}的通项公式 (2)若a(n)+3n-2=2/b(n),求数列{bn}的前n项和S(n)
a(n+1)=an+2n
an - a(n-1)=2(n-1)
an - a1 = 2( 1+2+...+(n-1))
= n(n-1)
an = n^2-n+2
an+2n-2 = 2/bn
bn = 2/(an+2n-2)
=2/(n^2+n)
= 2[ 1/n -1/(n+1) ]
Sn = b1+b2+...+bn
=2( 1- 1/(n+1) ]
= 2n/(n+1)
公共课灌灌灌灌灌灌灌灌灌灌灌灌灌灌灌灌灌灌灌f76i869i67i6y