Theorems

https://en.wikipedia.org/wiki/Theory_(mathematical_logic) https://en.wikipedia.org/wiki/List_of_first-order_theories https://en.wikipedia.org/wiki/First-order_logic https://en.wikipedia.org/wiki/Mathematical_logic https://en.wikipedia.org/wiki/Category:Conceptual_systems https://en.wikipedia.org/wiki/Category:Inductive_reasoning https://en.wikipedia.org/wiki/Category:Abstraction https://en.wikipedia.org/wiki/Category:Formal_theories https://en.wikipedia.org/wiki/Category:Logical_expressions

https://infinityplusonemath.wordpress.com/2017/03/11/a-mathematical-intro-to-special-relativity/#fnref-1528-Einstein

https://en.wikipedia.org/wiki/Theory_(mathematical_logic)

Fermat's Last Theorem

Fermat's Last Theorem states the absence of non-trivial integer solutions to the equation:

$x^n + y^n = z^n$

Namely, it seemed there are no integer solutions except for the trivial ones that set $n$ to 1

This is easily stated but has proved to be one of the most vexing problems in the whole history of mathematics.

and the search for a proof led to the development of whole new branches of mathematics, but it was only in the last decade of the 20th century that Andrew Wiles finally completed the task.