Bonjour,
1)
B = (3x+1)(6x-9)-(2x-3)² =
B =18x²-27x+6x-9-(4x²-12x+9 ) =
B =18x²-27x+6x-9-4x²+12x-9 =
B = 14x²-9x-18
2)
(6x-9) = 3(2x-3)
B = 3(3x+1)(2x-3)-(2x-3)² =
B = (2x-3)(3(3x+1)-(2x-3)) =
B = (2x-3)(9x+3-2x+3) =
B = (2x-3)(7x+6)
3)
si B = 0
(2x-3)(7x+6) = 0
(2x-3) = 0 2x = 3 x = 3/2
(7x+6) = 0 7x = -6 x = -6/7
