Square $ABCD$ is cut by a line segment $EF$ into two rectangles $AEFD$ and $BCFE$. The lengths of the sides of each of these rectangles are positive integers. It is known that the area of the rectangle $AEFD$ is $30$ and it is larger than the area of the rectangle $BCFE$. Find the area of square $ABCD$.
Proposed by Bogdan Rublov
Solução: Como [AEFD] = 30, então o lado do quadrado vale 6 e o outro lado de AEFD vale 5. Assim, FC = 1 e sua área vale 1 x 6 = 6. Logo, a area do quadrado [ABCD] = 36.