9: It was seen previously that the fourth root behaves like
n1/2, 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 n, so the whole denominator behaves (when n grows
large) like n3/2, 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 n in the second term in the
denominator and the root of n 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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Answer