Past Papers’ Solutions  Cambridge International Examinations (CIE)  AS & A level  Mathematics 9709  Pure Mathematics 1 (P19709/01)  Year 2015  OctNov  (P19709/12)  Q#2
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Question
In the expansion of , where k is a nonzero constant, the coefficients of and are equal. Find the value of k.
Solution
Expression for the general term in the Binomial expansion of is:
We are given the expression for expansion as;
First we rewrite the expression in the standard form;
In the given case:
Hence;
Since we are looking for the terms with : we can equate;




Now we can find the two terms with ;
Substituting ; 
Substituting ; 














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