Is $f (x) = - 2 x^{3} - 5 x^{2} - 6 x - 1$ $f(x)=-2x^3-5x^2-6x-1$ increasing or decreasing at $x = 1$ $x=1$ ?

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Answer 1 · 2016-01-09T04:18:52

DECREASING

The given function $f (x) = - 2 x^{3} - 5 x^{2} - 6 x - 1$ $f(x) = -2x^3- 5x^2 - 6x-1$ at $x = 1$ $x=1$

take the first derivative and then evaluate it at $x = 1$ $x=1$

$f' (x)= -6x^2-10x-6$

at $x=1$

$f' (1)=-6(1)^2-10(1)-6$

$f' (1)=-6-10-6$

$f' (1) = -22$ Negative sign means DECREASING

Is f(x)=-2x^3-5x^2-6x-1f(x)=−2x3−5x2−6x−1f(x)=-2x^3-5x^2-6x-1 increasing or decreasing at x=1x=1x=1?