Zidan is using the Rational Root Theorem to help find the roots of a 5th degree polynomial. He has discovered five roots and still has 4 to test. What is his next best step?

This size running track is usually called a 400 meter track. however if a person ran as close to the inside as possible on the track they would run less than 400 meters in one lap. how far away from the inside border would someone have to run to make one lap equal exactly 400 meters