Each week Manhattan GMAT posts a GMAT question on our blog and follows up with the answer the next day. Are you up for the challenge?
A function f(x) is defined as idempotent if, for every possible x, f(f(x)) = f(x). Which of the following functions is NOT idempotent?
(A) f(x) = x
(B) f(x) = –x
(C) f(x) = |x|
(D) f(x) = the greatest integer less than or equal to x
(E) f(x) = the least integer greater than or equal to x