What this sign mean (upward and downward arrows in 'limit' expressions)

That downward arrow must mean "approaching from the right." And the
upward arrow must mean "approaching from the left."
 
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narcislb said:
Hi, i am new here.I have a question about what those arrow mean?
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I had never seen it before, but it means just what I initially guessed: a limit from above or from below. See Wikipedia. This notation may be specifically used in your country, or in your field, or just in your book; I would expect them to have defined it somewhere.
 
Much more common are \(\displaystyle \lim_{x\to a^+}\) for "the limit as x approaches a from above" (or "from the right") and \(\displaystyle \lim_{x\to a^-}\) for "the limit as x approaches a from below" (or "from the left").
 
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