Im just not sure how to do this.

Heres my problem:

Discuss whether or not the given function is injective, surjective, and/or bijective.

f : N ⟶ Q, where f(n) = 1/n

g : X ⊆ R³ ⟶ R³, where g(x,y,z) = e^√(x²+ y²+z²-4)

h : X ⊆ R³ ⟶ R³, where h(x) = 2x/||x||₂

Thanks