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Example 10 Show that the function f : N → N, given by f (1) = f (2) = 1 and f (x) = x – 1, for every x > 2, is onto but not one-one. Here, f(x) = {█( 1 for 𝑥=1@ 1 for 𝑥=2@𝑥−1 for 𝑥>2)┤ Here, f (1) = 1 f (2) = 1 Check onto f: N → N f(x) = {█( 1 for 𝑥=1@ 1 for 𝑥=2@𝑥−1 for 𝑥>2)┤ Let f(x) = y , such that y ∈ N Here, y is a natural number & for every y, there is a value of x which is a natural number Hence f is onto

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Davneet Singh

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 13 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.