Let :

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- Aug 26th 2009, 03:06 PM #1

- Joined
- Aug 2008
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- 172

- Aug 26th 2009, 03:41 PM #2
I find it difficult to understand why this question is posted in an advanced forum.

I will let you work out this fact: $\displaystyle \left( {\exists N} \right)\left[ {n \geqslant N\, \Rightarrow \,\left| {x_n + 3} \right| < 7} \right]$.

Note that: $\displaystyle \left| {x_n ^2 - 9} \right| = \left| {x_n + 3} \right|\left| {x_n - 3} \right|$

It follows from that fact.