Bonjour,
4)
a) 3x + 27 = 3 (x + 9)
b) 7x - 42 = 7 (x - 6)
c) 9x + 9 = 9 (x + 1)
5)
a) 5a + 2a + 7b + 5b = 7a + 12b
b) 7x - 2x + 5y + 6y = 5x + 11y
c) 5x² + 7 + 2x + 3x² + 3x + 12 = 5x² + 3x² + 2x + 3x + 7 + 12 = 8x² + 5x + 19
d) 9x² - 4x - 6x² - 8 + 12x + 15 = 9x² - 6x² - 4x + 12x - 8 + 15 = 3x² + 8x + 7.
