Past Papers’ Solutions  Edexcel  AS & A level  Mathematics  Core Mathematics 1 (C16663/01)  Year 2013  June  Q#4
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Question
A sequence is defined by
, for
Where is a constant.
a) Find an expression for in terms of k.
Given that ,
b) Find the two possible values of k.
Solution
a)
We are given that sequence is defined by
We are required to find
We can utilize the given expression for general terms beyond first term as;
b)
We are given that;
It is evident that sum of first 3 terms of given arithmetic sequence is 2.
We are already given first term and have found 2^{nd} term in (a) while we need to find 3^{rd} term.
We can utilize the given expression for general terms beyond first term as;
We can substitute
Therefore;
As per given condition
Now we have two options.









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