What are fluents?

Answer

Given:

$f(x) = 3x^2*dx/dt -4x*dx/dt -3y*dy/dt$

the fluent of f is

$int f(x)*dt = int (3x^2*dx/dt *dt -4x*dx/dt *dt -3y^2*dy/dt*dt)$

thus the equation for fluent is

$int (3x^2*dx -4x*dx -3y^2*dy) =0$

$3x^3/3 -4x^2/2 -3y^3/3 =0$

$x^3 -2x^2 -y^3 =0$