Muft Shiksha
Update

Muft Shiksha™ एक 100% Free Education Portal है 🇮🇳, जिसका उद्देश्य Class 9–12 के हर विद्यार्थी तक High-Quality Education को पूरी तरह मुफ्त पहुँचाना है। 🇮🇳 हम मानते हैं कि अच्छी शिक्षा किसी student की आर्थिक स्थिति पर निर्भर नहीं होनी चाहिए। 🇮🇳 हर विद्यार्थी को वही Quality Study Material, MCQs, Quizzes, Exam Preparation, Concept-Based Learning और Bilingual Support मिलना चाहिए, जो आमतौर पर महंगी Coaching या Premium Platforms में मिलता है। Muft Shiksha™ 🇮🇳 इसी सोच के साथ बनाया गया है

Subjects
Class 9MathematicsSequences and ProgressionsExplicit or general ruleHardLevel 49
0 reads0 ratings0 helpful

If (a_n=2n+1) and (b_n=n^2-1), what is (a_4+b_4)?

Advertisement

Answer and explanation

Correct answer: 24

Substitute n=4 into both rules. \(a_4=2(4)+1=9\) and \(b_4=4^2-1=15\). Therefore, \(a_4+b_4=9+15=24\). A result such as 26 comes from evaluating one of the terms incorrectly. Exam tip: find each sequence term separately before adding them.

Related tags

SequencesProgressionsExplicit RuleNth TermSubstitution

Frequently asked questions

What is the correct answer to this question?

24

Why is this the correct answer?

Substitute n=4 into both rules. \(a_4=2(4)+1=9\) and \(b_4=4^2-1=15\). Therefore, \(a_4+b_4=9+15=24\). A result such as 26 comes from evaluating one of the terms incorrectly. Exam tip: find each sequence term separately before adding them.

Which subject and chapter does this question cover?

This is a Class 9 Mathematics question. Chapter: Sequences and Progressions. Topic: Explicit or general rule.

Was this question useful?

No ratings yetWrite a review / Rate this question

Student Reviews

No published reviews yet.

KEEP PRACTISING

10 more MCQs
  1. 1For the sequence 2, 5, 10, 17, 26, ..., the nth term is a_n = n² + 1. What is the value of a_12 − a_10?
  2. 2For the sequence 6, 14, 26, 42, ..., a_n = 2n² + 2n + 2. What is the value of a_15 - a_13?
  3. 3If a_n = (-1)^n(n + 1), what will be the value of a_7 + a_8?
  4. 4What will be the next term in the sequence (1, 2, 6, 24, 120, …)?
  5. 5If a_n = 5n + (−1)^n, what will be the value of a_10 − a_9?
  6. 6If a_n = 4n^2 + 2n - 3, what will be the value of a_11?
  7. 7If a_n = (-1)^(n+1)(2n+3), what will be the value of a_8 + a_9?
  8. 8If a_n = n^2 + 6n + 5, which term is 252?
  9. 9What is the general term of the sequence (3, 6, 9, 12, …)?
  10. 10Which explicit rule is correct for the sequence (5, 10, 15, 20, …)?
Advertisement