voila l'exercice il faut factorisez ces exprssion a = 6x + 72 b = 14x - 42 c = 36x + 20

a= 6x +72
  = 6*x +6*12
  = 6(x+12)
  

b= 14x -42
  = 7*2x -7*2
  = 7(2x -2)
    ou
b= 14x -42
  = 14 *x -14*3
  = 14(x -3)

c= 36x +20
  = 4*9x +5*4
  = 4(9x +5)