Please answer both of the questions :D

Which of the following is best modeled using a linear equation y=ax+b, where a is less than 0?

The circle below is centered at the point (3, 1) and has a radius of length 2. what is the equation?

Can you me with this question? i'll reward *30 points i just need with this one question so that i could solve the others. * edit: i originally set up the question to reward 30 points, but for some reason i can only reward 15. if you don't get 30, then i'm sorry. i'm still kind of new to this site