http://www.phengkimving.com/calc_of...l/11_03_tests_for_conv_of_improper_intgrl.htm pics View attachment 7236 Ok the question is he said that if we cannot find g(x) or h(x) such that the conditions specified there is obeyed, then the standard comparison test will not work Is there exist any method (similar to how one can show and prove that some integrals cannot be expressed as elementary functions) that can tell us that such g or h exist/do not exist even in principle, despite we might not be able to came up with it immediately probably because the g,h is a complicated expression?