Show that the function `f: N->N` , given by `f(x)=2x` , is one-one but not onto.

Explanation

To show that the function \( f: \mathbb{N} \to \mathbb{N} \) defined by \( f(x) = 2x \) is one-one but not onto, we will follow these steps:

### Step 1: Prove that \( f \) is one-one (injective)

To prove that \( f \) is one-one, we need to show that if \( f(x_1) = f(x_2) \), then \( x_1 = x_2 \).

1. Assume \( f(x_1) = f(x_2) \).
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