bonjour
( x + 2 ) ( x - 3 ) = x² - 3 x + 2 x - 6 = x² - x - 6
( 2 x + 1 ) ( x + 5 ) = 2 x² + 10 x + x + 5 = 2 x² + 11 x + 5
( 3 x - 1 ) ( 3 x + 4 ) = 9 x² + 12 x - 3 x - 4 = 9 x² + 9 x - 4
(2 a - 1 ) ( 3 a - 5 ) = 6 a² - 10 a - 3 a + 5 = 6 a² - 13 a + 5
