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Question
Check the injectivity and surjectivity of the following function:
f : N → N given by f(x) = x3
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Solution
f : N → N given by f(x) = x3
It is seen that for x, y ∈ N, f(x) = f(y)
⇒ x3 = y3
⇒ x = y
∴ f is injective.
Now, 2 ∈ N, but there does not exist any element x ∈ N such that f(x) = x3 = 2.
∴ f is not surjective
Hence, function f is injective but not surjective.
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