Write an emacs/lisp program (Provide proof it works)

Write a function that takes one parameter that is a list of numbers and returns true (t) if all the elements of the list are multiples of the first one and nil otherwise. This said, a list generated by the function make-multiples could be passed to this new function and the result should be true. On the other hand, show an example of a list that could not have been generated by the first function for which the result is still true.