a(n+1)= an/(4an+1)
1/a(n+1) = (4an +1)/an
=4 + 1/an
1/a(n+1)-1/an =4
=>{1/an }是等差数列,d=4
1/an -1/a1 =4(n-1)
1/an = 4n-3
an = 1/(4n-3)
bn =1/an = 4n-3
a(n+1)= an/(4an+1)
1/a(n+1) = (4an +1)/an
=4 + 1/an
1/a(n+1)-1/an =4
=>{1/an }是等差数列,d=4
1/an -1/a1 =4(n-1)
1/an = 4n-3
an = 1/(4n-3)
bn =1/an = 4n-3