Which describes $f(x) = - x^{3} - x + 4$ ?

Strictly increasing on

\mathbb{R}

Correct answerYour answerIncreasing on one part of

\mathbb{R}

and decreasing on anotherCorrect answerYour answerStrictly decreasing on

\mathbb{R}

Correct answerYour answerConstant on

\mathbb{R}

Correct answerYour answer

Show the answer and explanation

CorrectNot quiteAnswer C

Correct answer: C

$f'(x) = - 3 x^{2} - 1$ .
Here $-3x^2 - 1 < 0$ for every $x$ , so $f$ is strictly decreasing on $\mathbb{R}$ .

Ten questions from Increasing & Decreasing Functions, at your own pace.

Ten questions from Increasing & Decreasing Functions, at your own pace.

Which describes f(x)=−x3−x+4f(x) = - x^{3} - x + 4f(x)=−x3−x+4?