Réponse :
ex 1
E = (3x + 1)²-(3x + 1)(2x - 1)
1) E = 9x^2 + 6x + 1 - (6x^2 - 3x + 2x - 1)
E = 9x^2 + 6x + 1 - 6x^2 + 3x - 2x + 1
E = 3x^2 + 7x + 2
2) E = (3x + 1) (3x + 1 - 2x + 1)
E = (3x + 1) (x + 2)
3) a) E = (3 x 0 + 1) (0 + 2)
E = 1 x 2
E = 2
b) E = (3 x 2/3 + 1) (2/3 + 2)
E = 3 x 8/3
E = 8
ex 2
AB^2 + AC^2 = BC^2
AC^2 = BC^2 - AB^2
AC^2 = (x + 7)^2 - 5^2
AC^2 = x^2 + 14x + 49 - 25
AC^2 = x^2 + 14x + 24
