В=5а^3 если а=3х-4
B = [m]5(3x-4)^3[/m] [m](a-b)^3=a^3 - 3a^2 b + 3ab^2-b^3[/m] B = [m]5(27x^3-108x^2+144x-64)[/m] = [m]135x^3-540x^2+720x-320[/m]