问题描述: 已知函数f(x)=x^2-4x+2,数列{an}是等差数列,且a1=f(x+1),a2=0,a3=f(x-1),求通项公式an与前n项和Sn. 1个回答 分类:数学 2014-10-03 问题解答: 我来补答 a2-a1=a3-a2-(x+1)^2+4(x+1)-2 = (x-1)^2-4(x-1)+22x^2+2-8x+4=0x^2-4x+3=0x=1 or 3if x=1a1=f(2)=4-8+2=-2a3=f(0) =2an = -2+(n-1)2 = 2n-4Sn = n(a1+an)/2 = n(n-3)if x=3a1=f(4)=16-16+2=2a3=f(2)=4-8+2=-2an =2-2(n-1) =4-2nSn= (3-n)n 展开全文阅读