bonsoir
x² + 4 x - 1 = ( x - 1) ( x - 2 )
x² + 4 x - 1 = x² - 2 x - x + 2
x² - x² + 4 x + 2 x + x = 2 + 1
7 x = 3
x = 3/7
( x - 2)² = ( x + 3 )²
x² - 4 x + 4 = x² + 6 x + 9
x² - x² - 4 x - 6 x = 9 - 4
- 10 x = 5
x = - 5/10 = - 1/2
( x + 7)² = x² - 49
x² + 14 x + 49 = x² - 49
x² - x² + 14 x = - 49 - 49
14 x = - 98
x = - 7