bonjour
A = x² + 6 x - x = x² + 5 x
B = xy - x + xy = 2 xy - x
C = 3 x² + 12 x - 6 x² = - 3 x² + 12 x
D = 9 x ³ - 54 x + 2 x²
E = 15 x + 25 x² + 5 x + x² + 8 x² + 4 x = 34 x² + 24 x
F = 21 x² - 35 x - 48 x - 42 x² = - 21 x² - 83 x
G = 27 + 81 x + 28 x² - 48 x ³ + 55 x - 88 x²
= - 48 x ³ - 60 x² + 81 x + 27
