bonsoir
a = 25 x² - 30 x + 9 - 4 x - 8 = 25 x² - 34 x + 1
b = 2 x + 10 + x² + 16 x + 64 = x² + 18 x + 74
c = 4 - (25 x² + 10 x + 1) = 4 - 25 x² - 10 x - 1 = - 25 x² - 10 x + 3
d= 18 x + 6 - ( 49 x² - 42 x + 9) = 18 x + 6 - 49 x² + 42 x - 9 = - 49 x² + 60 - 3
e= (2 x + 1 + 2 x - 1) ( 2 x + 1 - 2 x + 1) = (4 x ) ( 2) = 8 x
f) 4 x² - 20 x + 25 + 4 x² - 6 x + 6 x - 9 = 8 x² - 20 x + 16