You can
put this solution on YOUR website! If v=log(base 2)(1/4), by definition of log,
2^v = 4.
Now if v= -2, 2^(-2) = 1/2^2 = 1/4
So your answer is correct.
One way to solve:
v = log(base 2)(1/4) = -log(base 2)4 = -log(base 2) 2^2
= - 2 log(base 2) 2 = -2 * 1 = -2.