bonjour
C = 45 - 18 x² + 18 x² - 48 x - 3 x + 8
= - 51 x + 53
D = 6 x² - 3 x - 10 x + 5 - ( 9 x² - 30 x + 25 )
= 6 x² - 13 x + 5 - 9 x² + 30 x - 25
= - 3 x² + 17 x - 20
