1/non car 30.3>30
1/ 49 - 8 * 6 = 49 - 48 = 1
2/ 100 - 11 * 9 = 100 - 99 = 1
3/ 16 - 5 * 3 = 16 - 15 = 1
4/ 9 - 4 * 2 = 9 - 8 = 1
5/ 625 - 26 * 24 = 625 - 624 = 1
6/ 13 - 4 * 3 = 13 - 12 = 1
21 - 5 * 4 = 21 - 20 = 1
7/ tous ces opérations sont égaux
8/
[tex]x {}^{2} - ( x+ 1)(x - 1) \\ = {x}^{2} - {x }^{2} - 1 {}^{2} = \\ = 1[/tex]
