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If the explicit rule of a sequence is (a_n=pn^2+qn+1) and the first two terms are (6) and (15), what is the value of (a_4)?
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Answer and explanation
Correct answer: (45)
From the given terms, (p+q=5) and (2p+q=7), so (p=2), (q=3), and (a_4=45). When coefficients are unknown, first form equations using small terms.
Frequently asked questions
What is the correct answer to this question?
(45)
Why is this the correct answer?
From the given terms, (p+q=5) and (2p+q=7), so (p=2), (q=3), and (a_4=45). When coefficients are unknown, first form equations using small terms.
Which subject and chapter does this question cover?
This is a Class 9 Mathematics question. Chapter: Sequences and Progressions. Topic: Explicit or general rule.
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