4. Efectuați calculele:
a) [(2x + 3)(x - 3) - x(x - 4) +9] : x;
c) x(2x - y) - (2x + y)[4x - 3(x - y)];
e) y(4x - 3y) + (x - y)[5x - 3(x + y)].
b) [(x + 2)(x + 3) - x(x + 6)](x - 1);
d) (x + 2)[7x - 4(x - 1)] - 27x4 : (-3x)";​