Question 3

Jambmaths question: 

Find the derivative of $y={{(\tfrac{1}{3}x+6)}^{2}}$

Option A: 

$2(\tfrac{1}{3}x+6)$

Option B: 

$\tfrac{2}{3}(\tfrac{1}{3}x+6)$

Option C: 

$\tfrac{2}{3}{{(\tfrac{1}{3}x+6)}^{2}}$

Option D: 

$\tfrac{1}{3}{{(\tfrac{1}{3}x+6)}^{2}}$

Jamb Maths Solution: 

$\begin{align}  & y={{[f(x)]}^{n}} \\ & \text{Using the generalised derivative formula} \\ & \frac{dy}{dx}=n\times {{[f(x)]}^{n-1}}\times f'(x) \\ & y={{(\tfrac{1}{3}x+6)}^{2}} \\ & \frac{dy}{dx}=2\times [(\tfrac{1}{3}x+6)]\times \tfrac{d}{dx}(\tfrac{1}{3}x+6) \\ & \frac{dy}{dx}=2[(\tfrac{1}{3}x+6)]\times \tfrac{1}{3}=\tfrac{2}{3}(\tfrac{1}{3}x+6) \\ & \frac{dy}{dx}=\tfrac{2}{3}(\tfrac{1}{3}x+6) \\\end{align}$ 

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