MCQ
$2{x^3} - 6x + 5$ is an increasing function if
  • A
    $0 < x < 1$
  • B
    $ - 1 < x < 1$
  • $x < - 1$ or $x > 1$
  • D
    $ - 1 < x < - 1/2$

Answer

Correct option: C.
$x < - 1$ or $x > 1$
c
(c) Let $f(x) = 2{x^3} - 6x + 5$ ==> $f'(x) = 6{x^2} - 6 > 0$

==> ${x^2} - 1 > 0$==> $(x - 1)$ $(x + 1) > 0$

==>$x > 1$ or $x < - 1$.

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