The function $f(x)= -2x^3-9x^2-12x+5$ is :
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → increasing in (-2, -1) and decreasing in (-∞,-2) ∪ (-1, ∞)
$f(x)=-2x^3-9x^2-12x+5$
$f'(x)=-6x^2-18x-12=0$
$⇒-x^2-3x-2=0$
so $-(x+2)(x+1)=0$
$x=-1,-2$
Using wavy curve
$f(x)$ increasing in (-2, -1) and decreasing in (-∞,-2) ∪ (-1, ∞)