voici le résultat

a) a = 3 x + 6  = 3 ( x +2)

b = 5x - 10 = 5 (x - 2)

c = 4x + 9 x = x (4 + 9 )

d = 12 + 18 x = 6 ( 2 + 3 x)

e = 50 - 10 x = 10 (5 - x)

f = x²-7x = x( x + 7)

g = 4x² - 20 x = 4x(x - 5 )

h = 3x² - 5 x = x(3x - 5)

i = 12 x² - 3 = 3(4 x²-1)

b)  a = 7x - 7 = 7 (x - 1 )

b=3x² + 3 x = 3x (x + 1 )

c = 18 x - 9x = 9 (2x -x)

d = 10 - 20 x = 10( 1 - 2x)

e = 4x² - 9x = x (4x -9)

f = 10 x ² + 35 x = 5x (2x + 7)