bonjour
a = 4 ( x² + 1)
b = 2 ( 4 - a)
c = 5 x ( y - 2)
A = - 7 x + 14
B = 4 x² + 12 x + 5 x + 15 = 4 x² + 17 x + 15
C ) 27 x² - 9 + 3 x² - x = 30 x² - x - 9
d = 30 x² - 18 x - 10 x + 6 = 30 x² - 28 x + 6
B - C
= 4 x² + 17 x + 15 - ( 30 x² - x - 9)
= 4 x² + 17 x + 15 - 30 x² + x +9
= - 26 x² + 18 x + 24
A- B+ C - D
- 7 x + 14 - ( 4 x² + 17 x + 15) + 30 x² - 28 x + 6 - ( 30 x² - 28 x + 6)
= - 7 x + 14 - 4 x² - 17 x - 15 + 30 x² - 28 x + 6 - 30 x² + 28 x - 6
= - 4 x² - 24 x - 1