MCQ
If the real valued function $f(x)=\frac{a^x-1}{x^x\left(a^x+1\right)}$ is even, then n equals
  • A
    2
  • B
    $\frac{-2}{3}$
  • C
    $\frac{1}{4}$
  • $-\frac{1}{3}$

Answer

Correct option: D.
$-\frac{1}{3}$
(D)
Since $f (x)$ is even, $f (-x)= f (x)$
$\therefore \quad \frac{ a ^{-x}-1}{(-x)^{ n }\left( a ^{-x}+1\right)}=\frac{ a ^x-1}{x^{ n }\left( a ^x+1\right)}$
$\Rightarrow \frac{1- a ^x}{(-1)^{ n } x^{ n }\left(1+ a ^x\right)}=\frac{ a ^x-1}{x^{ n }\left( a ^x+1\right)}$
$\Rightarrow \frac{-1}{(-1)^{ n }}=1 \Rightarrow-1=(-1)^{ n }$
$\therefore \quad n =-\frac{1}{3}$ can satisfy the equation.

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