Smallest positive number whose y-th power is divisible by x
Brachylog, 19 17 16 15 12 bytes
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:[I:1]*$r=#&gt;

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Explanation
               Input = [X, Y]
:[I:1]*        Get a list [X*I, Y] (I being any integer at this point)
       $r=     Get the first integer which is the Yth root of X*I
          #&gt;   This integer must be strictly positive
               This integer is the Output