Question

Which of the following represents identity function?

• A. $f:R\to R,f\left(x\right)=-x$
• B. $f:R\to R,f\left(x\right)=2x$
• C. $f:R\to R,f\left(x\right)=x$
• D. $f:Z\to Z,f\left(x\right)=x$

Answer 1

Answer: (C), (D)

$f:Z\to Z,f\left(x\right)=x$

For identity function input is always equal to output. i.e. it always gives the same value as its input.
Identity function is $f\left(x\right)=x$