Pythagoras's theorem, that in a right angled triangle,
a2 + b2 = c2
where c is the hypotenuse and a and b are the other two sides is easy to state and its proof has been known for centuries.
Fermat's last theorem is analogous but opposite, and is equally easy to state:
For any index (power) greater than 2, the analogy of Pythagoras's theorem has no integer solution (other than trivial ones eg a = 0 or b = 0).
Solving Fermats theorem.
Andrew Wiles solved/proved Fermats Last Theorem. The theorem states Xn + Yn = Zn , where n represents 3, 4, 5,......... there is no solution.
Fermat's last theorem states that the equation xn + yn = zn has no integer solutions for x, y and z when the integer n is greater than 2. When n=2, we obtain the Pythagoras theorem.
Fermat's Last Theorem is sometimes called Fermat's conjecture. It states that no three positive integers can satisfy the equation a*n + b*n = c*n, for any integer n greater than two.
Although the Pythagorean theorem (sums of square of a right angled triangle) is called a theorem it has many mathematical proofs (including the recent proof of Fermats last theorem which tangentially also prooves Pythagorean theorem). In fact Pythagorean theorem is an 'axiom', a kind of 'super law'. It doesn't matter if anyone does oppose it, it is one of the few fundamental truths of the universe.
But it was. That is why we know about it. If you mean why the PROOF was not written- Fermat wrote that he had found a wonderful proof for the theorem, but unfortunately the margin was too small to contain it. This is why the theorem became so famous- being understandable by even a schoolchild, but at the same time so hard to prove that even the best mathematicians had to surrender, with a simple proof seemingly being existent that just nobody except Fermat could find. The theorem has since been proven but the proof uses math tools that are very advanced and were not available in Fermat's life-time.
While the theorem is attributed to Pythagoras, there is reason to believe it was known much earlier. For example, megalithic sites that predate Pythagoras seem to have applied this knowledge.
to make something seem easy.
beside its very convenient and easy to follow with, almost all high, low, and machine languages instruction are formulated to comply with the structure theorem.
You can find an introduction to Stokes' Theorem in the corresponding Wikipedia article - as well as a short explanation that makes it seem reasonable. Perhaps you can find a proof under the links at the bottom of the Wikipedia article ("Further reading").
Norton's theorem is the current equivalent of Thevenin's theorem.
You cannot solve a theorem: you can prove the theorem or you can solve a question based on the remainder theorem.