Bonjour,

A = (x+3)(x+5)-3(x+5)

   = (x+5)[(x+3)-3]

   = (x+5)(x)

B = (2x+3)(x-4)+(3x-5)(x-4)

  = (x-4)[(2x+3)+(3x-5)]

  = (x-4)(5x-2)

C = (3x-1)(x-2)-(2x+5)(3x-1)

   = (3x-1)[(x-2)-(2x+5)]

   = (3x-1)(-x-7)

   = -(3x-1)(x+7)

D = x(2x+3)-7(2x+3)

   = (2x+3)(x-7)

E = (x+1)(x+7)-(x+7)

  = (x+1)(x+7)-1(x+7)

  = (x+7)[(x+1)-1]

  = (x+7)(x)

F = (2x-5)²-(2x-5)(x+2)

  = (2x-5)(2x-5)-(2x-5)(x+2)

  = (2x-5)[(2x-5)-(x+2)]

  = (2x-5)(x-7)

G = 2x+1+5x(2x+1)-3x(2x+1)

   = 1(2x+1)+5x(2x+1)-3x(2x+1)

   = (2x+1)[1+5x-3x)

   = (2x+1)(2x+1)

   = (2x+1)²

H = (x-8)²+(x-8)

   = (x-8)(x-8)+(x-8)1

   = (x-8)[(x-8)+1]

   = (x-8)(x-7)