A) 0 and 0
B) x = 1 and ? 1
C) x = 1 and ? 3
D) x = ? 1 and 3
Correct Answer: D
Solution :
\[y={{x}^{3}}-3{{x}^{2}}-9x+5\] Þ \[\frac{dy}{dx}=3{{x}^{2}}-6x-9.\] We know that this equation gives the slope of the tangent to the curve. The tangent is to parallel to x-axis, \[\therefore \]\[\frac{dy}{dx}=0\]. Therefore \[3{{x}^{2}}-6x-9=0\] Þ \[x=-1,\,3\].You need to login to perform this action.
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