∵a(n+1)+2an+3=0
∴a(n+1)=-2an-3
∴[a(n+1)+1]/(an+1)
=(-2an-3+1)/(an+1)
=(-2an-2)/(an+1)
=-2(an+1)/(an+1)
=-2(常数)
∴数列{an+1}是等比数列
∵a(n+1)+2an+3=0
∴a(n+1)=-2an-3
∴[a(n+1)+1]/(an+1)
=(-2an-3+1)/(an+1)
=(-2an-2)/(an+1)
=-2(an+1)/(an+1)
=-2(常数)
∴数列{an+1}是等比数列