For some reason, it only works for certain combinations of countries and languages. E.g., it works for Argentina: http://www.bing.com/search?q=x-3%2fx-1%3dx-4%2fx-5&setmk... but not Chile: http://www.bing.com/search?q=x-3%2fx-1%3dx-4%2fx-5&setmk...