If f is an invertible function, defined as f(x) = , then write
Let A = {1, 2, 3, 4}. Let R be the equivalence relation on A × A defined by (a, b)R(c, d) if a + d = b + c. Find the equivalence class [(1,3)].
If f : R → R is defined by f(x) = 3x + 2, then define f [f(x)].