Merci de preciser les etapes dans la reponse

Ex 27 :

4x + 8 = 4(x + 2)
7x + 21 = 7(x + 3)
2 - 16x = 2(1 - 8x)
x² + 8x = x(x + 8)

Ex 28 :

3x + 3 = 3(x + 1)
9t + 9 = 9(t + 1)
4 - 4y = 4(1 - y)
1,2 + 1,2r = 1,2(1 + r)