Answer :
To prove: function is one-one and into
Given: f: N → N : f(x)= 3x
We have,
f(x) = 3x
For, f(x1) = f(x2)
⇒ 3x1 = 3x2
⇒ x1 = x2
When, f(x1) = f(x2) then x1 = x2
∴ f(x) is one-one
f(x) = 3x
Let f(x) = y such that
⇒ y = 3x
If y = 1,
But as per question , hence x can not be
Hence f(x) is into
Hence Proved
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