Discrete Math Homework.... Help?

Question

Determine whether the functions
a) f(x) = 3x - 1
b) f(x) = x^3 - x
are one to one and onto over the integers, the rationals, and the real numbers.

Answer 1

a) Suppose f(x) = f(y). Then 3x - 1 = 3y - 1, and x = y. Therefore this is 1-1 on all three sets.

b) f(-1) = f(0) = f(1) = 0. This is not 1-1 on any of your domains.