4: to clear the radical on the bottom you multiply the top and the bottom by the bottom: so the answer would be D.
5: You need to simplify 112: 7 and 16. 16 is a perfect square so you bring out 4 and multiply -11 by 4: so the answer is A.
6: to add or subtract radical expressions with the same radical you just add or subtract the whole number: So the answer would be 17-9= 8√17
:) hope this helps :)
