Past Papers’ Solutions | Cambridge International Examinations (CIE) | AS & A level | Mathematics 9709 | Pure Mathematics 1 (P1-9709/01) | Year 2017 | May-Jun | (P1-9709/13) | Q#1

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The coefficients of  and  in the expansion of  are equal. Find the value of the non-zero  constant a.


We need to equate the coefficients of  and  in the expansion of given expression. 

We are given expression as;

Expression for the general term in the Binomial expansion of  is:

In the given case:


Since we are looking for the coefficients of and : we can  proceed as follows;

For coefficient of ;

For coefficient of ;

Substituting 1;

Substituting ;

We are given that coefficients of  and  in the expansion of  are equal. Therefore;