Bonjour,
Ex. 2 :
3y + 9y = y(3+9) = 12y
3y - 9y = y(3-9) = -6y
3y² + 9y² = y²(3+9) = 12y²
3z + 9y = 3(z+3y)
Ex.3 :
4x² + 2x - (3x + 4x² - 9) + 8 = 4x² + 2x - 3x - 4x² + 9 + 8 = 17 - x
8x - 5x(2 - x) = 8x - 10x + 5x² = 5x² - 2x
-3(2x - 5) - (-2x + 7) = -6x + 15 + 2x - 7 = 8 - 4x
