P(x)=a0+a1x+⋯+a2011x2011+x2012
Nigel and Jessica are playing the following game. In turn, they choose one of the coefficients a0,⋯,a2011 and assign a real value to it. Nigel has the first move. Once a value is assigned to a coefficient, it cannot be changed any more. The game ends after all the coefficients have been assigned values.
Jessica's goal is to make P(x) divisible by a fixed polynomial m(x) and Nigel's goal is to prevent this.
Which of the players has a winning strategy if m(x)=x2+1?
This problem has been answered by Mark as well!
Below is what Mark has provided for us:
We see that:
m(±i)=0
So, in light of the cyclical nature of integral powers of i, let us define:
r≡1005∑k=0((−1)ka2k)+1
s≡1005∑k=0((−1)k+1a2k+1)
And so we now see that:
P(i)=r+si
P(−i)=r−si
Since Jessica requires that P(±i)=0, she needs to ensure that r=s=0. And so a winning strategy for Jessica is to always follow Nigel with a pick of coefficients in the same sum (either r or s) with the same number but with a subscript of opposing parity to produce a pair adding to zero. When Nigel picks his last coefficient in the sum within r, Jessica needs to subtract 1 from his choice as her last pick in this sum. She could actually choose to subtract 1 from any of Nigel's choices as one of her choices within r.
In this way, Jessica can ensure her winning strategy.
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