设等差数列公差为d.数列共n+2项.
2n+4=2+(n+1)d
d=(2n++4-2)/(n+1)=(2n+2)/(n+1)=2
d=f(a1)-2=loga(a1)-2=2 loga(a1)=4 a1=a^4
f(an)-f[a(n-1)]=loga(an)-loga[a(n-1)]=loga[an/a(n-1)]=2
an/a(n-1)=a²,为定值.
数列{an}是以a^4为首项,a²为公比的等比数列.
an=a^4×(a²)^(n-1)=a^(2n-2+4)=a^(2n+2)
设等差数列公差为d.数列共n+2项.
2n+4=2+(n+1)d
d=(2n++4-2)/(n+1)=(2n+2)/(n+1)=2
d=f(a1)-2=loga(a1)-2=2 loga(a1)=4 a1=a^4
f(an)-f[a(n-1)]=loga(an)-loga[a(n-1)]=loga[an/a(n-1)]=2
an/a(n-1)=a²,为定值.
数列{an}是以a^4为首项,a²为公比的等比数列.
an=a^4×(a²)^(n-1)=a^(2n-2+4)=a^(2n+2)