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Differentiation Question A level maths

I'm not sure If I've done part A and B right? I feel like i've done little working out for part a since its 5 marks? And more for part B and its 2 marks? I'm pretty sure I've gone wrong somewhere.

(edited 2 years ago)

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Reply 1

username1732133

Original post by ExamSeason12

I'm not sure If I've done part A and B right? I feel like i've done little working out for part a since its 5 marks? And more for part B and its 2 marks? I'm pretty sure I've gone wrong somewhere.

I'm not sure what you have done but it's clear that you haven't shown that k = 6.

In part (a) you need to differentiate twice and use the definition of a point of inflection.

(edited 2 years ago)

Reply 2

username5737602

I'm sorry but that first solution made me laugh. Not tryna be rude. But for part a point of inflection occurs when d2y/dx2 =0. So basically do what you did for part b then sub in x=1 and rearrange to get k=6. And for b you just sub in 0.5and 1.5 to the original equation and show there is a sign change