3rd term : a + 2d = -9 .......(1) 7th term : a + 6d = -29 ......(2) (2) - (1): 4d = -20 :. d = -20/4 = -5 From (1) : a + 2(-5) = -9 a - 10 = -9 :. a = -9 + 10 = 1 :. 10th term of A.P is a + 9d = 1 + 9 (-5) = 1 - 45 = -44
