Bonsoir,
A = (2x – 5)2 + (x - 9)(3x - 6)
= 4x -10 + 3x² -6x -27x +64
= 3x² -29x +54
B = 7x² - 9 - (x + 4)(5x - 7)
7x² -9 -( 5x² -7x +20x -28)
= 7x² -9 - 5x² +7x +20x +28
= 2x² +27x +19
C = (5x - 8)2 + (6x + 2)²
10x -16 + 36x² +24x +4
= 36x² +34x -12
D = (4x + 5)(4x – 5) - (3x - 6)(7x + 2)
= 16x² -25 -(21x² +6x -42x -12)
= 16x² -25 -21x² -6x +42x +12
= - 5x² -36x -13