数列满足a1+a2+……+an=2n^2-3n+1 ,求a4+a5+a6+.+an
问题描述:
数列满足a1+a2+……+an=2n^2-3n+1 ,求a4+a5+a6+.+an
答
a4+a5+a6+.+an=(a1+a2+……+an)-(a1+a2+a3)=(2n^2-3n+1)-(2*3^2-3*3+1)=2n^2-3n-9
数列满足a1+a2+……+an=2n^2-3n+1 ,求a4+a5+a6+.+an
a4+a5+a6+.+an=(a1+a2+……+an)-(a1+a2+a3)=(2n^2-3n+1)-(2*3^2-3*3+1)=2n^2-3n-9