1.

Let f ∶ N→ N such that f(x) = 2 for all . x \(\in\) N Show that f is one-one and into.

Answer»

We have function defined on such that f(x) = 2x ∀ x∊N . 

Let x1, x2 ∊ N such that x1 ≠ x2

⇒ 2x1 ≠ 2x2 (By multiplying by 2 both sides of equation. ) 

⇒ f(x1) ≠ f(x2). 

Hence, different elements have different images under the function . 

This implies each element of connected with different elements (even numbers) of under the function , therefore, function f(x) is one-one function. 

Let f(x) = 3 ∊ N. 

⇒ 2x = 3 ⇒ x = \(\frac{3}{2}\)∉ N . 

Hence, 3 ∊ N does not have pre-image under the function f, therefore, function f(x) is an into function. 

No odd numbers have pre-image of function . 

Hence, function f ∶ N → N such that f(x) = 2x is one-one and into function.



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