I can do the first bit, which is just manipulation of the LHS, but I'm not sure how to start on the second and third bit.

Say we wish to estimate the square rot of 2. We begin with a good first estimate

, say

. In fact, it is a little too big. We note that 2/1.5 is a little too small, so we form a new guess by averaging them,

. We continue this method to give a sequence:

To ease notation, we set

, so,

i) Show that

;

ii) show that

iii) How big do we require

so that

is within

of

. Find the

**fraction**