No need to expand up to x³.

Oops, I expanded first because I not sure what question 1b actually asked for.

Usually they tend to ask three or four, and here they actually didn’t specify (even though we know only the first two terms are needed), so for the benefit of the doubt, I gave four terms.

This question is similar to binomial expansion so not sure why she couldn't get the answer (unless expanded wrongly)


Sonia, it would be better if you provided the first part so as to set the context for the second part (that you are asking for)

Well, it’s possible that the binomial skills learnt in A Maths has been partially forgotten already.

One of my students who have completed the full syllabus of A Maths two months ago actually forgot how to do logarithms learnt in Sec 3.

But this one is Maclaurin's series, a topic that is recently taught for JC1/Year 5. The expansion formulas are all in MF26 and would have been covered. Even if the student doesn't see the similarity to binomial theorem, applying the formula should be a piece of cake.