Graph the six terms of a finite series where a1 = -3 and r = 1.5.

A1 is the 1st term 
r is the difference, they can say "r" or "d" for the difference 

1st a1 is the first term = -3
2nd "r" is the difference between each consecutive terms (coming after each other) = 1.5
the rule to get any term of the sequence as we add 1.5 each time is --> a1+(n-1)*d 
a1 --> 1st term , n --> order of the term u want whether 2nd, 3rd , 25th 
d --> difference 
so to get the 2nd-->    -3+(2-1)*1.5= -1.5
to get the 3rd -->        -3 +(3-1)*1.5 = 0 
and so on 

Yes, two vertical lines can be complementary