(1)f(x1),f(x2),...,f(xn),...是公差为2的等差数列,且x1=a*2所以f(xn)=loga(a^2)+2(n-1)=2n因f(xn)=loga(xn)所以{xn}=a^(2n)(2)由(1)和a=1/2得x1+x2+.+xn=(1/2)^2+(1/2)^4+...+(1/2)^(2n)=(1/4)(1-(1/4)^(n))/(1-(1/...