proving an inequality involving limit superior and limit inferior

Question

how can I show that $$\limsup_{n\to\infty} (a_n + b_n) \geq \limsup_{n\to\infty}(a_n) + \liminf_{n\to\infty}(b_n)$$

See also this question: Properties of $\liminf$ and $\limsup$ of sum of sequences — Martin Sleziak, Mar 25 '12 at 09:08

score 5 · Accepted Answer · answered Mar 22 '12 at 01:59

5

Use $\limsup_n (x_n+y_n) \le \limsup_n x_n + \limsup_n y_n$, with $x_n = a_n+b_n$ and $y_n = -b_n$.

answered Mar 22 '12 at 01:59

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