2an+a(n-1)=3,a1=2
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2an+a(n-1)=3,a1=22an+a(n-1)=3,a1=22an+a(n-1)=3,a1=22an+a(n-1)=3an=-(1/2)*a(n-1)+3/2所以an-1=-(1/2)*a(n
2an+a(n-1)=3,a1=2
2an+a(n-1)=3,a1=2
2an+a(n-1)=3,a1=2
2an+a(n-1)=3
an=-(1/2)*a(n-1)+3/2
所以an-1=-(1/2)*a(n-1)+3/2-1=-(1/2)*a(n-1)+1/2=(-1/2)*[a(n-1)-1]
所以当n≥2时数列{an-1}是等比数列,公比是q=-1/2
所以an-1=(a1-1)*(-1/2)^(n-1)=(2-1)*(-1/2)^(n-1)=(-1/2)^(n-1)
那么an=2 (n=1)
=1-(-1/2)^(n-1)(n≥2)
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