B = (5 - x/2)(2x - 4)
B = (5 - x/2*2)(2x - 4)
B = (5 - x)(2x - 4)
B = 10x - 20 - 2x² + 4x
B = -2x² + 14x - 20
C = (9 - 6x)(-2 + 2x/3)
C = (9 - 6x)(-2 + 2x/3*3)
C = (9 - 6x)(-2 + 2x)
C = -18 + 18x + 12x - 12x²
C = -12x² + 30x - 18
D = (12a - 18)(1/4 + 2x/3)
D = (12a - 18)(1/4 + 2x/3*3)
D = (12a - 18)(1/4 + 2x)
D = 3a + 24ax - 4,5 - 36x
