Which best describes the relationship between the successive terms in the sequence shown?

9, –1, –11, –21, …

athe common difference is –10.
bthe common difference is 10.
cthe common ratio is –9.
dthe common ratio is 9.

Dean and karlene get paid to write songs. dean is paid a one-time fee of $20 plus $80 per day. karlene is paid a one-time fee of $25 plus $100 per day. write an expression to represent how much a producer will pay to hire both to work the same number of days on a song.