The fourth term in an arithmetic sequence is 18 and the seventh term is 39. If the first term is a1 , which is an equation for the nth term of this sequence?

i believe it is c.y = 9x

rise over run. 9 units up over 1 unit right or 9/1

in geometry, parallel lines are lines in a plane which do not meet; that is, two lines in a plane that do not intersect or touch each other at any point are said to be parallel. by extension, a line and a plane, or two planes, in three-dimensional euclidean space that do not share a point are said to be parallel.

x:       y:  

-1         4

0         4

1         6

2         18

3         20