求解一道数列的题已知等差数列{an}的前n项和Sn=pn²-2n+q (p,q∈R).n∈N+(1)求q的值要详细步骤哦,捣乱的边去~
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![求解一道数列的题已知等差数列{an}的前n项和Sn=pn²-2n+q (p,q∈R).n∈N+(1)求q的值要详细步骤哦,捣乱的边去~](/uploads/image/z/446229-45-9.jpg?t=%E6%B1%82%E8%A7%A3%E4%B8%80%E9%81%93%E6%95%B0%E5%88%97%E7%9A%84%E9%A2%98%E5%B7%B2%E7%9F%A5%E7%AD%89%E5%B7%AE%E6%95%B0%E5%88%97%7Ban%7D%E7%9A%84%E5%89%8Dn%E9%A1%B9%E5%92%8CSn%3Dpn%26sup2%3B-2n%2Bq+%28p%2Cq%E2%88%88R%EF%BC%89.n%E2%88%88N%2B%281%29%E6%B1%82q%E7%9A%84%E5%80%BC%E8%A6%81%E8%AF%A6%E7%BB%86%E6%AD%A5%E9%AA%A4%E5%93%A6%2C%E6%8D%A3%E4%B9%B1%E7%9A%84%E8%BE%B9%E5%8E%BB%7E)
求解一道数列的题已知等差数列{an}的前n项和Sn=pn²-2n+q (p,q∈R).n∈N+(1)求q的值要详细步骤哦,捣乱的边去~
求解一道数列的题
已知等差数列{an}的前n项和Sn=pn²-2n+q (p,q∈R).n∈N+
(1)求q的值
要详细步骤哦,捣乱的边去~
求解一道数列的题已知等差数列{an}的前n项和Sn=pn²-2n+q (p,q∈R).n∈N+(1)求q的值要详细步骤哦,捣乱的边去~
[x]表示下标
A[n]=S[n]-S[n-1]=(pn^2-2n+q)-(p(n-1)^2-2(n-1)+q)=-2-p+2np
A[1]=-2-p+2p=p-2
A[1]=S[1]=p-2+q
则p-2=p-2+q
q=0