Q356 · Practice questionTechnology-freeComplex familiar4 marks
QUESTION 356 (4 marks)
The derivative of a function is . Determine the interval on which is both decreasing and concave up. Justify your answer.
a)[4 marks]
Show your reasoning.
WORKED SOLUTION
4 marksPractice marking scheme
ANSWER
.
Worked solution
exactly when . Differentiating gives exactly when . Intersecting these strict inequalities gives .
Exact answers unless rounding is specified; equivalent forms accepted. Retain unrounded intermediate values.
Finds the decreasing interval.
Determines the second derivative.
Finds the concave-up interval.
Intersects the intervals correctly.
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