Question 1010711
 If f(x) = (1/x - 9x) / (1+3x), what is f(1/x). 
f(1/x) = ((1/(1/x))-9(1/x)) / (1+3(1/x)) =
(x - (9/x)) / (1 + 3(1/x)) =
((x^2-9) / x) / ((x+3) / x)) =
(((x+3)(x-3)) / x) * (x / (x+3)) =
(x-3)