In order to solve this problem, you have to substitute x and y for each coordinate pair. which ever pair doesn't work with the equation is the answer.
y=3(1/2)^x
12=3(1/2)^-2 12=3(4) 12=12 (correct)
3/8=3(1/2)^3 3/8=3(1/8) 3/8=3/8 (correct)
3=3(1/2)^0 3=3(1) 3=3 (correct)
9=3(1/2)^-1 9=3(2) 9=6 (incorrect)
because 9≠6 we can see that (-1, 9) is the point that does not lie on the graphed equation