A = 5(a + 2) - (6a - 7)

   = 5*a + 5*2 - 6a + 7 = 5a + 10 - 6a + 7 = 5a - 6a + 10 + 7 = -a + 17

B = -b(3b + 7) + (5-b) x b

  = -b*3b -b*7 + b*5 + b*(-b) = -3b² - 7b + 5b - b² = -4b² - 2b

C=-c(4+3c) - (9-2c +6c²)

  = -4c - 3c² - 9 + 2c - 6c² = -9c² - 2c - 9

et

D = -5d + 5d(d-2) - 6(7-3d)

  = -5d + 5d² - 10d - 42 + 18d

  = 5d² + 3d - 42

puisque k(a+b) = ka + kb