4an-4n-2=2a(n-1)+2n+3-4n-2=2a(n-1)-2n+14[an-(n+1)+1/2]=2[a(n-1)-n+1/2][an-(n+1)+1/2]/[a(n-1)-n+1/2]=1/2所以an-(n+1)+1/2是等比数列,q=1/2你没有给a1an-(n+1)+1/2=[a1-(1+1)+1/2]*q^(n-1)=(a1-3/2)q^(n-1)所以...