Past Papers’ Solutions | Cambridge International Examinations (CIE) | AS & A level | Mathematics 9709 | Pure Mathematics 1 (P1-9709/01) | Year 2016 | Oct-Nov | (P1-9709/12) | Q#4
In the expansion of , the coefficient of x is 7. Find the value of the constant n and hence find the coefficient of .
Binomial Theorem states that if is a natural number;
First we expand .
In the given case:
We will have the given product as;
We consider only the terms containing ;
We are given that coefficient of the term with x is 7. Therefore, we can equate;
Next we need to find the coefficient of .
As we have expanded the given product above;
From here we take out the term containing .
As we have found above that ;
Hence coefficient of in the expansion of is .