Problem

You are told that $f(x)$ has a local max at $x=7$ and neither a local max nor a local min at $x=2$. Which of the following statements are consistent with this information? Select all that apply. Correct answers are worth 0.5 marks each, to a max of 1 mark on this question. Incorrect answers are worth -0.5 marks each, to a min of 0 marks on this question. A. $f^{\prime}(7)=0$ and $f^{\prime \prime}(7)=-5$ B. $f^{\prime}(2)=3$ and $f^{\prime \prime}(2)=0$ C. $f^{\prime}(2)=0$ and $f^{\prime \prime}(2)=-3$ D. $f^{\prime}(7)=5$ and $f^{\prime \prime}(7)=5$ E. $f^{\prime}(7)=-5$ and $f^{\prime \prime}(7)=-5$ F. $f^{\prime}(2)=0$ and $f^{\prime \prime}(2)=3$ G. $f^{\prime}(7)=0$ and $f^{\prime \prime}(7)=5$ H. $f^{\prime}(7)=-5$ and $f^{\prime \prime}(7)=0$

Solution

Step 1 :Given that $f(x)$ has a local max at $x=7$ and neither a local max nor a local min at $x=2$.

Step 2 :From the first derivative test, we know that if $f(x)$ has a local max at $x=a$, then $f^{\prime}(a)=0$.

Step 3 :From the second derivative test, we know that if $f(x)$ has a local max at $x=a$, then $f^{\prime \prime}(a)<0$.

Step 4 :So, the statement $f^{\prime}(7)=0$ and $f^{\prime \prime}(7)=-5$ is consistent with the given information.

Step 5 :Since $f(x)$ has neither a local max nor a local min at $x=2$, $f^{\prime}(2)$ can be any real number except 0.

Step 6 :Also, $f^{\prime \prime}(2)$ can be any real number.

Step 7 :So, the statement $f^{\prime}(2)=3$ and $f^{\prime \prime}(2)=0$ is consistent with the given information.

Step 8 :Final Answer: The statements that are consistent with the given information are \(\boxed{A}\) and \(\boxed{B}\).

From Solvely APP
Source: https://solvelyapp.com/problems/38136/

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