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Ex 8.2, 3
Last updated at June 9, 2026 by Teachoo
Class 9
Chapter 8 - Predicting What Comes Next: Exploring Sequences & Progress
- Definition
- Explicit Rule for a Sequence
- Recursive Rule for a Sequence
- Virahānka–Fibonacci sequence
- Exercise Set 8.1
- Arithmetic Progressions
- Visualising an AP
- Sum of the First n Natural Numbers
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Exercise Set 8.2
- Geometric Progressions
- Fractals as a GP Sequence
- Visualising a GP
- Exercise Set 8.3
- End-of-Chapter Exercises
Transcript
Ex 8.2, 3 Find the nth term of the AP 11, 8, 5, 2, …. Write the recursive rule for this AP. Given AP 11, 8, 5, 2, …. Here, First term = a = 11 Common difference = d = 8 – 11 = –3 We need to find the nth term So, we use the formula an = a + (n – 1) d Putting a = 11, d = –3 an = 11 + (n – 1) × (–3) = 11 + n × –3 – 1 × –3 = 11 – 3n + 3 = 14 – 3n Thus, nth term of AP is 14 – 3n Now, we asked Write the recursive rule for this AP A recursive formula tells you how to find the next term in a sequence by doing something to the previous term. It always requires two pieces of information The starting point (usually the first term, a) The rule to get from one term (an–1) to the next term (an) For our AP, our recursive formula is an = an–1 + d Putting d = –3 an = an–1 + (–3) an = an–1 – 3 Where a1 = a = 11 Note In recursive formula, we need the first term as well as the rule. Only rule is not a recursive formula
