locate the critical points of the following function. then use the second derivative test to determine…

locate the critical points of the following function. then use the second derivative test to determine whether they correspond to local maxima, local minima, or neither. f(x)=e^x(x + 6) what is(are) the critical point(s) of f? select the correct choice below and, if necessary, fill in the answer box to complete your choice. a. the critical point(s) is(are) x = -7. (use a comma to separate answers as needed.) b. there are no critical points for f. find f(x). f(x)=
Answer
Explanation:
Step1: Find the first - derivative
Use the product rule $(uv)^\prime = u^\prime v+uv^\prime$, where $u = e^{x}$ and $v=x + 6$. $u^\prime=e^{x}$, $v^\prime = 1$. So $f^\prime(x)=e^{x}(x + 6)+e^{x}=e^{x}(x + 7)$. Set $f^\prime(x)=0$, since $e^{x}\gt0$ for all $x\in R$, then $x+7 = 0$, so $x=-7$.
Step2: Find the second - derivative
Differentiate $f^\prime(x)=e^{x}(x + 7)$ using the product rule again. Let $u = e^{x}$, $v=x + 7$, $u^\prime=e^{x}$, $v^\prime = 1$. Then $f^{\prime\prime}(x)=e^{x}(x + 7)+e^{x}=e^{x}(x + 8)$.
Answer:
$f^{\prime\prime}(x)=e^{x}(x + 8)$