What is the missing term in the perfect square that starts with x^2-12x

How do you determine whether a relationship represented as as graph is linear or nonlinear

Expresa commuter train leaves downtown sation and travels at a average speed of 55 miles per hour towards the north side sation, which is 50miles away. thirty minutes later, express commuter train #7 leaves north side and travels at a average speed of 35miles per hour towards downtown sation. at the moment the two trains pass each other, how far(in miles) is train #12 from the downtown sation and how long(in minutes) has the #12 train been traveling

Find the greatest common factor of the followig monomials 21u^5v,3u^4v^6, and 3u^2v^5