10_Answer sheet of A.P. U-5 Part-4

16.  a(10)= 108
17. a= -1, d= 3, a(1)= -4, a(2)= -1,
      a(3)= 2
18. a(4)= 32^(1/2)
19.  n= 10th
20. n= 60, S(60)= 7800