I have this question here which I tried to do but I could not work out how to do part iii. After a while I tried look at the mark scheme as well but I still couldn't quite understand it. Why is it significant that k>i? Why must that be true for ai to be constant
#oxford maths entrance exam question
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$(1+x^k)P(x)=P(x)+x^kP(x)$
If you want to only look for the coefficient of $x^i$ where $i<k$, then that coefficient can be found in the $P(x)$ part of the sum
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why does this prove that a is constant for every degree of x in p(x)?
Essentially what you want to prove is that the coefficient of $x^i$ would eventually be as in $p_i(x)$
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$p_{i+1}(x)=(1+x^{i+1})p_i(x)=p_i(x)+x^{i+1}p_i(x)$
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and only the $p_i(x)$ part matters here
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ive been taking a while to think about it but im still not quite sure i understand
consider the coefficient of $x^i$ on both sides