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CUET · MATHS · PYQ PAPER 2023

Consider the function \(f: N \rightarrow N\) given by \(f(x)=\left\{\begin{array}{ll}x+1, & \text { if } x \text { is odd } \\ x-1, & \text { if } x \text { is even }\end{array}\right.\)

  1. A f is neither one-one nor onto
  2. B f is one-one but not onto
  3. C f is onto but not one-one
  4. D f is both one-one and onto
Verified Solution

Answer & Solution

Correct Answer

(D) f is both one-one and onto

Step-by-step Solution

Detailed explanation

One-one: Assume \(f(x_1) = f(x_2)\). If \(x_1\) is odd, \(f(x_1) = x_1+1\) (even). If \(x_2\) is even, \(f(x_2) = x_2-1\) (odd). These cannot be equal. Thus \(x_1, x_2\) must be of the same parity. If \(x_1, x_2\) both odd: \(x_1+1 = x_2+1 \implies x_1 = x_2\). If \(x_1, x_2\)…