Bonsoir,
A= 18x² - 3x
B= 8x -2x² -28 +7x = -2x² +15x -28
C= 5x - 7 -4x -2= x -9
D= 14 -2x
E:
x(4-7x)
F:
7( 3x+1)
G:
(4x -7) (4x+7) ( identité remarquable)
H:
(7-x) ( 5x+1 +2-3x) = (7-x) ( 2x +3)
5x+1 = 11
5x= 11-1
5x = 10
x= 10/5 = 2
4x-9 = 2x-3
4x-2x = -3+9
2x = 6
x = 6/2 = 3
x² = 21
x= √21 ou -√21