MCQ
Choose the correct answer from the given four options.
Let f : [0, 1] → [0, 1] be defined by $\text{f}(\text{x})=\begin{cases}\text{x, if x is rational}\\1-\text{x, if x is irrational}\end{cases}$ Then (fof)x is:
  • A
    constant
  • B
    1 + x
  • x
  • D
    none of these.

Answer

Correct option: C.
x
We are given that, f : [0, 1] → [0, 1] be defined by $\text{f}(\text{x})=\begin{cases}\text{x, if x is rational}\\1-\text{x, if x is irrational}\end{cases}$

Now, $(\text{fof})\text{x} = \text{f}(\text{f(x)})$

$=\text{x}$

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