Выражения 5a+(a--3) (x-4)(x-5)-2x(x-6) (c^2-3a)(3a+c^2)

1)5a+(a-4)-(2a-3)=5a+a-4-2a+3=4a-1
2)(x-4)(x-5)-2x(x-6)=х^2 - 5x - 4x + 20 - 2x^2 + 12x = - x^2 + 3x + 20
3)c^2-3a-9a^2-6ac-c^2=-9a^2-6ac-3a=-3a(a+2c+1)