bonjour
1² + 1 = 2 ² - 2
1 + 1 = 4 - 2
2 = 2
2 ² + 2 = 3 ² - 3
4 + 2 = 9 -3
6 = 6
7² + 7 = 8 ² - 8
49 + 7 = 64 - 8
46 = 46
42 ² + 42 = 43² - 43
1764 +42 = 1 849 - 43
1 806 = 1806
n ² + n = ( n + 1 )² - ( n + 1 )
n ² + n = n² + 2 n + 1 - n - 1
n ² + n = n² + n