The answer is A (3, 6)
plug it in: a of n(3) = (a of 2 which is 6)squared minus a of 2 which is 6.
you get: an(3)=36 minus 6 which equals 30
then plug it in for a of 4:
a of n(4) is 870=(a of 3 which is 30)squared minus a of three which is 30
so you get: 870=900 minus 30
that gives you the answer of 870=870 so answer #1 is correct