4: In the denominator, each term of the product should be investigated separately. In the first term, we saw before that the inside root behaves like x2 and the whole root behaves like x. Thus in the denominator, the first term in the product behaves like x, and the second like x2, so the denominator is of the type x3, just like the numerator. Thus it is possible to cancel this power in the fraction instead of factoring it out. However, here, because of the complicated roots, the best way is to pull the leading powers out step by step, start from the inside roots and work your way out.
By the way, we should be able to guess the answer using intuitive calculations: