Edexcel IAL WMA12/01/P2/Oct 2021/Q1 (Binomial Expansion)
The first three terms, in ascending powers of x, of the binomial expansion of
where k and p are constants.
Find, in simplest form,
the value of k
the value of p
(3)
Using the value of k found in part (a),
find the term in x2 in the expansion of g(x).
(3)
SOLUTION
i- Using binomial theorem to find the first 3 terms of the expression.
Hence, the expansion gives
Whereas it is given that the first three terms of the expansion are
Lets equate the second term to find the value of k.
ii- Equating the third term to find the value of p.
Hence,
b- The expression we found with the help of binomial expansion is
Lets substitute the value of
Therefore,
Hence, the term in x2 in the expansion of g(x) are
