Mathematics - Application of Derivative Question with Solution | TestHub

MathematicsApplication of DerivativeMonotonicity-Increasing-DecreasingMedium2 minPYQ_2019
MathematicsMediumsingle choice

If the functionfgiven byfx=x3-3a-2x2+3ax+7, for somea∈Ris increasing in0, 1and decreasing in1, 5, then a root of the equation,fx-14x-12=0, x≠1is :

Options:

Answer:
A
Solution:

Atx=1, f′x=0

∴ f′x=3x2-6a-2x+3a

Now, f'1=0

⇒3-6 a-2+3a=0

⇒a=5

∴ fx-14x-12=0

⇒x3-9x2+15x-7x-12=0

⇒x-7x2-2x+1x-12=0

⇒x-7=0⇒x=7

Stream:JEESubject:MathematicsTopic:Application of DerivativeSubtopic:Monotonicity-Increasing-Decreasing
⏱ 2mℹ️ Source: PYQ_2019

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