15: It was seen previously that the fourth root behaves like x^1/2, so this is also the order of the first term in the product in the denominator. The second term of this product is of the order x, so the whole denominator behaves (when x grows large) like x^3/2, which is also the order of the numerator. Thus it is also possible to cancel, the above analysis actually suggests that it is best to factor x in the second term in the denominator and the root of x in the first term.

As usual, slightly faster and easier way is to start by factoring out leading terms from the roots and then cancel.

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