Maxima Function
remfun (f, expr)
remfun(f,expr,x)
remfun (f, expr) replaces all occurrences of f (arg) by arg in expr.
f (arg)
remfun (f, expr, x) replaces all occurrences of f (arg) by arg in expr only if arg contains the variable x.
remfun (f, expr, x)