39: After simplification you should get
In this ratio of polynomials, the leading term in the numerator and the denominator is n. One possibility is to factor it out of the root and then out of the numerator and the denominator, it is also possible to cancel n in the fraction, one could also combine both ways: first factor out of the root, then factor. This is probably the easiest, but all three ways are about the same.
By the way, intuitive calculations should suggest the answer for a limit of this type:
