Fermat's Last Theorem
The proof was made for some'' values of , such as , ,  and , which was managed by many mathematicians including Fermat, Euler, Sophie Germain. However, since there are an infinite number of Pythagorean triples, as numbers count upwards forever, this made Fermat's Last Theorem hard to prove or disprove; the full proof must show that the equation has no solution for all values of  (when  is a whole number bigger than 2) but it is not possible to simply check every combination of numbers if they continue forever.