If f (1-2x) = 1-x ^ 2 / x ^ 2 (x is not equal to 0), then f (1 / 2)=___

If f (1-2x) = 1-x ^ 2 / x ^ 2 (x is not equal to 0), then f (1 / 2)=___

There is no need to calculate the function of F (x), and then substitute x = 1 / 2. The simplest way is to bring in the known relation f (1-2x) = 1-x ^ 2 / x ^ 2 when x = 1 / 4, then f (1-2 * 1 / 4) = f (1 / 2) = {1-1 / 16} * 16 = 15