bonsoir,
A: 3(4x+5)-5x(4x+5)
= 12 x + 15 - 20 x² - 25 x
= - 20 x² - 13 x + 15
B: (5x+2)(3x-4)
= 15 x² - 20 x + 6 x - 8
= 15 x² - 14 x - 8
C: (2x-7) ²
= 4 x² - 28 x + 49
D: (2x-3)(7+5x)-(4x-5)(2x-3)
= 14 x + 10 x² - 21 - 15 x - ( 8 x² - 12 x - 10 x + 15 )
= 10 x² - x - 21 - 8 x² + 22 x - 15
= 2 x² + 21 x - 36
