Question

Please help me on this question. thank you

Answer 1

L = a +nd
l'' =-2 when n=1
l = a +nd
-2=2 +d
d =-4

missing terms are  n=5 & n =6
accordingly 
n=5;                                          n=4;
l6=2 + 5(-4)                              l7=2+6.(-4)
   =-8//                                       l7 = -22//

Answer 2

For B the common differnce is positive 6 therefore it goes -17,-9,-3,3,9