 Later work has shown that the question of solvability of a Diophantine equation is undecidable even if the equation only has 9 natural number variables (Matiyasevich, 1977) or 11 integer variables (Zhi Wei Sun, 1992).Matiyasevich's theorem has since been used to prove that many problems from calculus and differential equations are unsolvable.One can also derive the following stronger form of Gödel's first incompleteness theorem from Matiyasevich's result