I want to use a function's derivative in an other function. How should this be done in Maxima?
E.g:
f(x) := 2*x^4;
g(x) := diff(f(x),x)-8;
Now g(x) yields 8x^3-8 as expected, but g(0) gives an error, since diff(f(0),0) doesn't make sense. But then how should I properly define g?