Bonjour
A = 3a (-4a + 5) - 7a + 6
A = - 12a ^{2} + 15a - 7a + 6
A = - 12a ^{2} + 8a + 6
B = (3a - 6) (2a + 7)
B = 6a ^{2} + 21a - 12a - 42
B = 6a ^{2} + 9a - 42
C = (-4a +5) (5a – 3) + 8a ^{2}
C = - 20a ^{2} + 12a + 25a - 15 + 8a ^{2}
C = - 12a ^{2} + 37a - 15