[Ans] (E)
[Question] What is the greatest positive integer x such that 4^x is a factor of 64^10?
Options:
(A) 5
(B) 9
(C) 10
(D) 20
(E) 30
[CoT] 64^10 = (4^3)^10 = 4^30

[Ans] (D)
[Question] A train 500 meters long completely crosses a 300 meters long bridge in 45 seconds. What is the speed of the train is?
Options:
(A) 32
(B) 28
(C) 49
(D) 64
(E) 21
[CoT] S = (500 + 300)/45 = 800/45 * 18/5 = 64

[Ans] (A)
[Question]

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
If f(x) = x^3/(x^4 - 1), what is f(1/x) in terms of f(x)?
Options:
(A) -f(x) 
(B) f(x) 
(C) 2*f(x) 
(D) 1/f(x) 
(E) 2/f(x) 
[CoT] If x = 2 then f(x) = 8/15 and f(1/x) = -8/15 which is equal to -f(x)