Bonsoir,
A(x) = (x + 3)² + (x + 3)(-2x +9)
(x+3) (x+3 -2x+9) =
(x+3) ( -x +12)
B(x) = (4x + 5)² – (2x + 9)(4x + 5)
(4x+5) (4x+5 -2x -9)=
(4x+5) 2x -4)
C(x) = (6 – x)(3x – 11) + (3x – 11)
(3x-11) (6-x +1)=
(3x-11 ) (-x +7)
D(x) = (5x – 6)(7 – 2x) – (5x – 6)²
(5x-6)( 7-2x -5x+6)=
(5x-6) ( -7x +13)