Check the injectivity and surjectivity of the function: $f : N\to N\; given\; by\; f(x)\; = x^2 $

Question

$\begin{array}{1 1} \text{injective} \\ \text{surjective} \\ \text{both injective and surjective} \\ \text{neither injective and surjective} \end{array} $