By what number (5/4)^6 should be divided to get (25/16)^8?

Name each raycalculation tip: in ray "ab", a is the endpoint of the ray.

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

Set $r$ is a set of rectangles such that (1) only the grid points shown here are used as vertices, (2) all sides are vertical or horizontal and (3) no two rectangles in the set are congruent. if $r$ contains the maximum possible number of rectangles given these conditions, what fraction of the rectangles in set $r$ are squares? express your answer as a common fraction.