r=2^(n+1), then in terms of r, 9^n=  Pick one:  A) r^2/81  B) r^2/9  C) r^2/4  D) r/3  E) r
Questions in terms of variables can be easily solved by plugging in some values: Say n = 0   r = 2^1 = 2   and you need the value of 2^n which is 2^0 = 1   So when you put r = 2 in the options, you should get 1. Only option (C) satisfies.   Answer (r^2/4)
<result>C</result>
r=2^(n+1), then in terms of r, 9^n=