Questo limite si calcola con la tecnica della "differenza di quadrati irrazionali":
lim
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4
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lim
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4
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4
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4
4
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lim
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4
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x
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4
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lim
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lim
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1
2
lim from{x toward 0 } {{ sqrt {4-x}-sqrt{x+4}} over { x } }=lim from{x toward 0 } {{ sqrt {4-x}-sqrt{x+4}} over { x } }cdot {{ sqrt {4-x}+sqrt{x+4}} over { { sqrt {4-x}+sqrt{x+4}} } }=lim from{x toward 0 } { {4-x-x-4} over {x cdot ( sqrt {4-x}+sqrt{x+4}) } }"=" newline "=" lim from{x toward 0 } { {-2x} over {x cdot ( sqrt {4-x}+sqrt{x+4}) } } =-2 cdot lim from{x toward 0 } { {1} over { sqrt {4-x}+sqrt{x+4} } }=-2 cdot { 1 over {sqrt 4 + sqrt 4} }=-2 cdot {1 over 4}= - {{ 1} over { 2}}