Exercice 11 : a) 13x + 9x = 22x /// b) 5y - 7y = -2y /// c) -3z - z = -4z /// d) 7a² - 3a² = 4a² /// e) b - 4b = -3b /// f) 3c + c - 2c = 4c - 2c = 2c ///\\\ Exercice 12 : a) 3x - 5 + 4x + 2 = 4x + 3x - 5 + 2 = 7x -3 \\\ b) -2y + 3 - 4y + 6 = -4y - 2y + 6 + 3 = -6y + 9 \\\ c) 5a + 7 - a + 7 = 5a - a + 7 + 7 = 4a + 14 \\\ d) 5b² + 3b - 2b - 3b² = 5b² - 3b² + 3b - 2b = 2b² + b
