Saved Bookmarks
| 1. |
The 19th term of an ap is equal to three times its 6th term. if the 9th term is 19 then a = ? |
|
Answer» Answer: a=3 Step-by-step explanation: let 1ST term = a and common difference = d 19th term = t19 = a + 18d 6th term = t6 = a + 5D 9th term = t9 = a + 8d = 19 (given) => a = 19 - 8d ----(1) also given, t19 = 3×t6 => a + 18d = 3×(a + 5d) = 3a + 15D => 3a - a - 18d + 15d = 0 => 2a - 3d = 0 => 2(19 - 8d) - 3d = 0 [from (1)] => 38 - 16D - 3d = 0 => 19d = 38 => d = 38/19 = 2 putting d in (1), a = 19 - 8d = 19 - 8×2 = 3 |
|