Tìm x, biết rằng: (x - 1)(x^2 + x + 1) - x(x - 2)(x + 2) = 5; (x - 1)^3 - (x + 3)(x^2 - 3x + 9) + 3(x + 4)(x - 4) = 2

Tìm x, biết rằng:
a/ (x - 1)(x^2 + x + 1) - x(x - 2)(x + 2) = 5
b/ (x - 1)^3 - (x + 3)(x^2 - 3x + 9) + 3(x + 4)(x - 4) = 2
c/ (x + 1)^3 - (x - 1)^3 - 6(x - 1)^2 = - 10