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If (a_n=10n+4), what is (a_{r+2})?
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Answer and explanation
Correct answer: \(10r+24\)
Given \(a_n=10n+4\), substitute \(n=r+2\): \(a_{r+2}=10(r+2)+4=10r+20+4=10r+24\). Hence, \(10r+24\) is correct. In \(10r+14\), the product \(10\times2=20\) has been handled incorrectly. Exam tip: always substitute the complete index expression in brackets.
Frequently asked questions
What is the correct answer to this question?
\(10r+24\)
Why is this the correct answer?
Given \(a_n=10n+4\), substitute \(n=r+2\): \(a_{r+2}=10(r+2)+4=10r+20+4=10r+24\). Hence, \(10r+24\) is correct. In \(10r+14\), the product \(10\times2=20\) has been handled incorrectly. Exam tip: always substitute the complete index expression in brackets.
Which subject and chapter does this question cover?
This is a Class 9 Mathematics question. Chapter: Sequences and Progressions. Topic: nth term.
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