Question 191900
Evaluate if possible 
3√ - 64 [cube root of -64] 
= -4 (principal cube root, there are 3)
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and 3√ 64 [cube root of 64]
= 4 (principal cube root, there are 3)
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 and √ -64 [sqrt(-64)] 
sqrt(-64) = +8i, -8i
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and √ 64 [sqrt(64) ]
= +8, -8