Bonjour,
A: 5x+10
= 5 (x + 2)
B: (x+2)(x+5)+9(x+2)
= (x + 2) (x + 5 + 9)
= (x + 2) (x + 14)
C: (x+2)(3x+4)+(x+2)(x-3)
= (x + 2) (3x + 4 + x - 3)
= (x + 2) (4x + 1)
D: (x+2)(8x-3)+3x+6
= (x + 2) (8x - 3) + 3 (x + 2)
= (x + 2) (8x - 3 + 3)
= (x + 2) (8x)
= 8x (x + 2)
E: (x+2)(2x+4)-(x-7)(x+2)
= (x + 2) [(2x + 4) - (x - 7)]
= (x + 2) (2x + 4 - x + 7)
= (x + 2) (x + 11)
F: (x+2)(9x-5)-8x-16
= (x + 2) (9x - 5) - 8 (x + 2)
= (x + 2) (9x - 5 - 8)
= (x + 2) (9x - 13)
G: 2(x+2)(x-4)+3(x+2)(x+8)
= (x + 2) (2x + 4 + 3x + 12)
= (x + 2) (5x + 16)
H: (x+8)(x+2)+x+2
= (x + 2) (x + 9)
I: (x+2)²+(x+2)(4x-9)
= (x + 2) (x + 2 + 4x - 9)
= (x + 2) (5x - 7)
J: (x+2)(x-2)+(2x-6)(3x+6)
= (x + 2) (x - 2) + 2 (x - 3)+ 3(x + 2)
= (x + 2) (x + 2x - 6 + x - 2 + 3x - 12)
= (x + 2) (7x - 20).