For the following identify whether the formula defines a function. If it is a function, identify whether it is one-to-one, onto, neither, or both (no proof is required): Let f A B be a function f is called one-to-one, or injective, if T2 f is called onto, or surjective, if f is called one-to-one correspondence, or bijective, if f is one-to-one and onto f_1: z rightarrow z f_1(x) = |x| f_2: N rightarrow Z f_2(x) = |x| f_2: Z rightarrow N f_2(x) = |x| f_3: N rightarrow N f_3(x) = |x|