Question 628477
If you mean:
{{{root(3,x)*root(5,4x)}}}
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You need a common index, similar to the common denomonator in fractions.
3*5 = 15
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{{{root(3,x)*root(5,4x) = root(15,x^5)*root(15,(4x)^3)}}}
= {{{root(15,64x^8)}}}