Q218 / 270 · NDA 2022 (Phase 1) · Mathematics

If $f(x)=4 x+3$, then what is $f^{\circ} f^{\circ} f(-1)$ equal to?

  • Correct answer
    A
    -1
  • B
    0
  • C
    1
  • D
    2

Solution

Given that $\mathrm{f}(\mathrm{x})=4 \mathrm{x}+3$ $\begin{aligned} & \therefore \text { fofo } \mathrm{f}(-1)=\mathrm{f}(\mathrm{f}(\mathrm{f}(-1))) \\ & =\mathrm{f}(\mathrm{f}(4(-1)+3))=\mathrm{f}(\mathrm{f}(-1)) \\ & =\mathrm{f}(4(-1)+3)=\mathrm{f}(-1)=4(-1)+3=-1\end{aligned}$

Hence, the correct answer is option: 'A'.

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