数列an=1,an=2a n-1 +13n,求an通项?
问题描述:
数列an=1,an=2a n-1 +13n,求an通项?
一定要构建等比数列,
答
an+(bn+c)=2a(n-1)+13n+bn+c=2[a(n-1)+(13+b)n/2+c/2]=2[a(n-1)+(13+b)(n-1)/2+(13+b+c)/2]所以b=(13+b)/2c=(13+b+c)/2所以b=13,c=26所以an+(13n+26)=2a(n-1)+26n+26=2[a(n-1)+13(n-1)+26][an+(13n+26)]/[a(n-1)+13(...