f(X)=logaX(a>0,a不等1),数列2,f(a1)...f(an),2n+4是等差数列,求an通项
问题描述:
f(X)=logaX(a>0,a不等1),数列2,f(a1)...f(an),2n+4是等差数列,求an通项
答
a太多了,换一个m,f(X)=logmX(m>0,m不等1),数列2,f(a1)...f(an),2n+4是等差数列,求an通项设b1=2,b2=f(a1),……,b(n+1)=f(an),b(n+2)=2n+4,bn=2+(n-1)db(n+2)=2+(n+1)d=2n+4(n+1)d=2n+2d=2bn=2+2(n-1)=nb(n+1)=f(an)=l...