a3=a1+2a2
q^2=1+2q
q^2-2q-1=0,
q=1±√2
因为等比数列{am}中,各项都是正数,所以公比为正数,即q=1+√2
(a9+a10)/(a7+a8)=a1*q^8(1+q)/[a1*q^6(1+q)}=q^2=3+2√2
a3=a1+2a2
q^2=1+2q
q^2-2q-1=0,
q=1±√2
因为等比数列{am}中,各项都是正数,所以公比为正数,即q=1+√2
(a9+a10)/(a7+a8)=a1*q^8(1+q)/[a1*q^6(1+q)}=q^2=3+2√2