2016 THREE(b)

Achievement
Question
Find the xx-value at which a tangent to the curve y=6xe3xy = 6x - e^{3x} is parallel to the xx-axis.

*You must use calculus and show any derivatives that you need to find when solving this
problem.*
Official Answer
y=6xe3xy=6x-e^{3x}
dydx=63e3x\dfrac{dy}{dx}=6-3e^{3x}

Want dydx=0\dfrac{dy}{dx}=0

3e3x=63e^{3x}=6
e3x=2e^{3x}=2
x=ln23=0.231x=\dfrac{\ln 2}{3}=0.231
Grading Criteria

Achievement (u)

  • Correct solution with correct derivative.

Merit (r)

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Excellence T1

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Excellence T2

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