Difference between revisions of "2010 AIME II Problems/Problem 10"

m (Created page with '== Problem 10 == Find the number of second-degree polynomials <math>f(x)</math> with integer coefficients and integer zeros for which <math>f(0)=2010</math>. ==Solution== ===Sol…')
 
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Burnside's Lemma:  
 
Burnside's Lemma:  
  
The answer is <math>\frac{3^4+1}{2}+\frac{3^4+1}{2}+3^4=\boxed{163}</math> -- it is group action of <math>\mathbb{Z}_2</math>.
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The answer is <math>\frac{3^4+1}{2}+\frac{3^4+1}{2}+3^4=\boxed{163}</math> -- it is group action of <math>\mathbb{Z}^2</math>.
  
 
== See also ==
 
== See also ==
 
{{AIME box|year=2010|num-b=9|num-a=11|n=II}}
 
{{AIME box|year=2010|num-b=9|num-a=11|n=II}}

Revision as of 19:16, 3 April 2010

Problem 10

Find the number of second-degree polynomials $f(x)$ with integer coefficients and integer zeros for which $f(0)=2010$.

Solution

Solution 1

Let $f(x) = a(x-r)(x-s)$. Then $ars=2010=2\cdot3\cdot5\cdot67$. First consider the case where $r$ and $s$ (and thus $a$) are positive. There are $3^4 = 81$ ways to split up the prime factors between a, r, and s. However, r and s are indistinguishable. In one case, $(a,r,s) = (2010,1,1)$, we have $r=s$. The other $80$ cases are double counting, so there are $40$.

We must now consider the various cases of signs. For the $40$ cases where $|r|\neq |s|$, there are a total of four possibilities, For the case $|r|=|s|=1$, there are only three possibilities, $(r,s) = (1,1); (1,-1); (-1,-1)$ as $(-1,1)$ is not distinguishable from the second of those three. Thus the grand total is $4\cdot40 + 3 = \boxed{163}$

Solution 2

Burnside's Lemma:

The answer is $\frac{3^4+1}{2}+\frac{3^4+1}{2}+3^4=\boxed{163}$ -- it is group action of $\mathbb{Z}^2$.

See also

2010 AIME II (ProblemsAnswer KeyResources)
Preceded by
Problem 9
Followed by
Problem 11
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
All AIME Problems and Solutions