For some integer , the polynomial has the three integer roots , , and . Find .
Problem 195
Official solution
From Vieta's formulas, we know that , and . Thus . All three of , , and are non-zero: say, if , then (which is not an integer). , let . If , then . We have
Thus . We know that , have the same sign. So .
Also, if we fix , is fixed, so is maximized when . Hence, \[2011 = a^2 - bc > \tfrac{3}{4}a^2 \qquad \Longrightarrow \qquad a ^2 4$,
is not divisible by , , which is too small to get .
, is not divisible by or or , we can clearly tell that is too much.
Hence, , . , .
Answer: