From pythagoras theorem The hypotenuse ( c ) is the side facing the right-angle. The longest side of the triangle. 152=122+|PQ|2 225=144+|PQ|2 225−144=|PQ|2 81=|PQ|2 A number when multiplied by itself, will give 81, which is 9 9×9=|PQ|2 Every number is raised to the power 1 91×91=|PQ|2 From the law of indices, am×an=am+n 91+1=|PQ|2 92=|PQ|2 Since the powers are the same, the bases should also be the same 9=|PQ|