bjr
a) 4 x "x"+ 4 x 7 => en commun : 4 => = 4(x+7)
b) x² + 2x = x*x+x*2 => en commun : x => = x(x+2)
c) 7x - 7 = 7*x - 7*1 => en commun : 7 => = 7(x-1)
d) 3x - 9 = 3*x - 3*3 => en commun : 3 => 3(x-3)
e) 10x + 20 = 10*x+10*2 => en commun : tu as compris
f) 9x² - 6x = 3x*3x - 3x*2 => en commun ; tu as compris