when we do differentiable equation, do we need to time the constant c by a number

for example,

case A: 2y=3x+c
is y=(3x/2)+c
case B: -3y=x+c
is y= (-x/3)+c
case C: -y=x+c
is y=-x-c

I don't know what you mean " need to time the constant c by a number"

It doesn't matter, since it is still a constant, if you take the derivative, the constant goes to zero anyway.