已知f(x)=logaX(a大于0,且a不等于1),若2,f(X1),f(X2),f(X3),,f(XN),2N+4,成等差数列求{AN}的通项公
问题描述:
已知f(x)=logaX(a大于0,且a不等于1),若2,f(X1),f(X2),f(X3),,f(XN),2N+4,成等差数列求{AN}的通项公
答
2,f(X1),f(X2),f(X3), ,f(Xn),2N+4,成等差数列(共n+2项)
设公差为d,则2n+4=2+(n+2-1)d
d=2
故f(xn)=2+nd=2n+2
即:loga(an)=2n+2
an=a^(2n+2)