-70a4 + 68a³ - 16a² First we look for a number we can factor out. The largest whole number that will divide evenly into 70, 68, and 16 is 2 and since the term with the largest exponent is negative we us -2. No we look for the largest power of a letter that we can factor out from all the terms. That's a² So we factor out -2a² and get -2a²(35a² - 34a + 8) Then we factor what's in the parentheses either by "the backwards FOIL trial and error" method or by the AC-method found here: http://www.algebra.com/my/change_this_name32371.lesson?content_action=show_dev -2a²(7a-4)(5a-2) Edwin