在数列{an}中,a1=1,a2=5,an+2=an+1-an (n∈N*), 则a100等于an+2=an+1-an,an+3=an+2-an+1, 两式相加可得an在数列{an}中,a1=1,a2=5,an+2=an+1-an (n∈N*), 则a100等于( )方法一: an+2=an+1-an,an+3=an+2-an+1, 两式相加

Question

在数列{an}中,a1=1,a2=5,an+2=an+1-an (n∈N*), 则a100等于an+2=an+1-an,an+3=an+2-an+1, 两式相加可得an
在数列{an}中,a1=1,a2=5,an+2=an+1-an (n∈N*), 则a100等于( )方法一: an+2=an+1-an,an+3=an+2-an+1, 两式相加可得an+3=-an,an+6=an, ∴a100=a16×6+4=a4=-1.这一步是什么意思?an+6=an, ∴a100=a16×6+4=a4=-1.为什么这样做?

Answer 1