I don't know how to write it with my keyboard so i try to explain
(4x4) + (3x3) = ?
It's the Pythagore relation .. You learn it in secondary 3 in math.
16 + 9 = 25
Now you have to do the " Racine Carré in french " so in english I think it's Square root but not sure So you need to do it to the 25
well don't know it by heart and don't have anything to calculate it but when you did it you should get the longer of the X