InterviewSolution
Saved Bookmarks
| 1. |
Show that each one of the following progressions is a G.P. Also, find the common ratio in each case:(i) 4, -2, 1, -1/2, ….(ii) -2/3, -6, -54, ….(iii) a, 3a2/4, 9a3/16, ….(iv) 1/2, 1/3, 2/9, 4/27, … |
|
Answer» (i) 4, -2, 1, -1/2, …. Let a = 4, b = -2, c = 1 In GP, b2 = ac (-2)2 = 4(1) 4 = 4 So, the Common ratio = r = -2/4 = -1/2 (ii) -2/3, -6, -54, …. Let a = -2/3, b = -6, c = -54 In GP, b2 = ac (-6)2 = -2/3 × (-54) 36 = 36 So, the Common ratio = r = -6/(-2/3) = -6 × 3/-2 = 9 (iii) a, 3a2/4, 9a3/16, …. Let a = a, b = 3a2/4, c = 9a3/16 In GP, b2 = ac (3a2/4)2 = 9a3/16 × a 9a4/4 = 9a4/16 So, the Common ratio = r = (3a2/4)/a = 3a2/4a = 3a/4 (iv) 1/2, 1/3, 2/9, 4/27, … Let a = 1/2, b = 1/3, c = 2/9 In GP, b2 = ac (1/3)2 = 1/2 × (2/9) 1/9 = 1/9 So, the Common ratio = r = (1/3)/(1/2) = (1/3) × 2 = 2/3 |
|