是a(n+1)=2an/(an +1)吧a(n+1)=2an/(an +1)1/a(n+1)=(an +1)/(2an)=(1/2)(1/an) +(1/2)1/a(n+1) -1=(1/2)(1/an) -(1/2)=(1/2)(1/an -1)[1/a(n+1) -1]/(1/an -1)=1/2,为定值.1/a1 -1=1/(2/3) -1=3/2-1=1/2数列{1/an -...