MCQ
If $f(x) = {\log _a}x$ and $F(x) = {a^x}$, then $F[f(x)]$ is
  • $f[F(x)]$
  • B
    $f[F(2x)]$
  • C
    $F|f(2x)|$
  • D
    $F[(x)]$

Answer

Correct option: A.
$f[F(x)]$
a
(a) $F\,[f(x)] = F\,({\log _a}x) = {a^{{{\log }_a}x}} = x$

$f\,[F\,(x)] = f({a^x}) = {\log _a}{a^x} = x\,{\log _a}a = x$.

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