Consider the function f(x)=x3−9x2−21x−2.Its derivative is f′(x)=3x2−18x−21. help (formulas)its second derivative is f′′(x)=6x−18The graph that correctly displays f(z) (in black) and f′′(x) (in orange) isABc0.B.Using the graphs of f and f′′, indicate where f is concave up and concave down. Enter DNE if such an interval does not exist: f is concave up on ◻ help (intervals).f is concave down on
Q. Consider the function f(x)=x3−9x2−21x−2.Its derivative is f′(x)=3x2−18x−21. help (formulas)its second derivative is f′′(x)=6x−18The graph that correctly displays f(z) (in black) and f′′(x) (in orange) isABc0.B.Using the graphs of f and f′′, indicate where f is concave up and concave down. Enter DNE if such an interval does not exist: f is concave up on ◻ help (intervals).f is concave down on
Identify Second Derivative: Identify the second derivative of the function f(x). The second derivative of the function f(x) is given as f′′(x)=6x−18.
Find Critical Points: Find the critical points of the second derivative.To find the intervals of concavity, we need to determine where the second derivative changes sign. This occurs at the critical points of the second derivative. Set f′′(x)=0 and solve for x:6x−18=06x=18$x = \(3\)
Test Intervals for Concavity: Test the intervals around the critical point to determine concavity.\(\newline\)We have one critical point, \(x = 3\). We will test the intervals \((-\infty, 3)\) and \((3, \infty)\) to see where the second derivative is positive (indicating concave up) and where it is negative (indicating concave down).\(\newline\)Choose a test point \(x = 2\) for the interval \((-\infty, 3)\):\(\newline\)\(f''(2) = 6(2) - 18 = 12 - 18 = -6\)\(\newline\)Since \(f''(2) < 0\), the function is concave down on the interval \((-\infty, 3)\).\(\newline\)Choose a test point \(x = 4\) for the interval \((3, \infty)\):\(\newline\)\((-\infty, 3)\)\(0\)\(\newline\)Since \((-\infty, 3)\)\(1\), the function is concave up on the interval \((3, \infty)\).
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