Math Gold Medalist

Lor

2023 AIME I 

Problem 15

Find the largest prime number $p<1000$ for which there exists a complex number $z$ satisfying

  • the real and imaginary part of $z$ are both integers;
  • $|z|=\sqrt{p},$ and
  • there exists a triangle whose three side lengths are $p,$ the real part of $z^{3},$ and the imaginary part of $z^{3}.$

Complex Numbers

Triangle Inequality

Factorization

Inequality

Modular Arithmetic

z = a + bi

Prove that Im{z^3}+Re{z^3}>p.sqrt(p)>p

Calculate Im{z^3} and Re{z^3} in terms of a, b

Consider Im{z^3}, Re{z^3}>0

Prove that abs(Im{z^3}-Re{z^3})<p=a^2+b^2

case1) a>0 -> b>0

case2) a<0, b>0 -> b=-a -> p=2

W.L.O.G a,b>0

Prove that a>max{b.sqrt(3), b/sqrt(3)}

Consider a=bk then k>sqrt(3)

   Solution