Which describes $f(x) = x^{3} + 2 x$ ?

Strictly increasing on

\mathbb{R}

Correct answerYour answerStrictly decreasing on

\mathbb{R}

Correct answerYour answerIncreasing on one part of

\mathbb{R}

and decreasing on anotherCorrect answerYour answerConstant on

\mathbb{R}

Correct answerYour answer

Show the answer and explanation

CorrectNot quiteAnswer A

Correct answer: A

$f'(x) = 3 x^{2} + 2$ .
Here $3x^2 + 2 > 0$ for every $x$ , so $f$ is strictly increasing 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+2xf(x) = x^{3} + 2 xf(x)=x3+2x?