We know the 3,4,5 right triangle That is, the Pythagorean triple (3,4,5) where and we know So we have which has solutions (a,b) = (4,1) or (4,7) which has solutions (a,b) = (3,-1) or (3,7) which has solutions (a,b) = (0,5) or (5,0) which has only solution (a,b) = (5,5) Edwin