MCQ
$(x + 1)$ is a factor of $x^n+1$ only if:
  • $n$ is an odd integer
  • B
    $n$ is an even integer
  • C
    $n$ is a negative integer
  • D
    $n$ is a positive integer

Answer

Correct option: A.
$n$ is an odd integer

If $x+1$ is a factor of $x^n+1$
then, at $x=-1, x^n+1=0$
$(-1)^n+1=0$
$(-1)^n=-1$
$(-1)^{\mathrm{n}}$ will be equal to $-1$ if and only if $n$ is an odd integer.
If $n$ is even, then $(-1)^{\mathrm{n}}=1$
So, $n$ should be an odd integer.

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