Integration +c being forgotten

Too many forgetting the + c in integration

question2
dy/dx=2x(x-3)
dy/dx=2x^2-6x
y=2/3x^3-3x^2

What about the + c
y=2/3x^3-3x^2 + c

To find the value of c use the point provided (3,6) x = 3 and y = 6
so c can be found

What about a question with v= and distance is required integrate yes but do not forget the +c

b)TO find the total distance travelled u need to integrate the (V) velocity.
v = 5t -3t^2 + 2
s= 5/2t^2 - t^3 + 2t

it must be
s= 5/2t^2 - t^3 + 2t + c