已知数列{an}满足:,a₁=-2,an+1=2an+n,则an的通项为?
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已知数列{an}满足:,a₁=-2,an+1=2an+n,则an的通项为?
已知数列{an}满足:,a₁=-2,an+1=2an+n,则an的通项为?
已知数列{an}满足:,a₁=-2,an+1=2an+n,则an的通项为?
设[a(n+1) +X(n+1)+y]=2[an+Xn+y]
即有a(n+1)=2an + Xn- X + y=2an + n
所以X=1,y=1
代回,所以数列{an+n+1}是以2为公比,0为首项的等比数列
所以an+n+1=0即an=-n-1