(99^2-98^2)/197+(98^2-97^2)/195+(97 ^2-96^2)/193+ ... +(2^2-1^2)/3
plz help

Select the best attribute for the angle pair formed by two parallel lines intersected by a transversal.

Which is a true statement about an exterior angle of a triangle a. it is formed by two segments that are not sides of the triangle, b. it forms a linear pair with one of the interior angles of the triangle, c. it is complementary to one of the interior angles of the triangle. d. it is formed by two segments that are sides of the triangle.

[10 points, algebra 2-simplifying complex fractions]according to my answer key the restrictions are -1 and 4. but why not positive 1?