Bonsoir,
A = (2x - 3)(7 - x)
A = 14x - 2x^2 - 21 + 3x
A = -2x^2 + 17x - 21
B = (x + y)(2x - y)
B = 2x^2 - xy + 2xy - y^2
B = 2x^2 + xy - y^2
C = (x - 7)(2 + y)
C = 2x + xy - 14 - 7y
D = (x - 1)(1 - x)
D = x - x^2 - 1 + x
D = -x^2 + 2x - 1
E = 3(3a + 4)^2
E = 3(9a^2 + 24a + 16)
E = 27a^2 + 72a + 48
F = -5(4 - b)^2
F = -5(16 - 8b + b^2)
F = -80 + 40b - 5b^2