2 x^3 - 6x + 5 is an increasing function if - Vidyadip

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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