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An arithmetic sequence has (a_n=2n+9). What is its first term?
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Answer and explanation
Correct answer: 11
To find the first term, put n=1. Thus, a_1=2(1)+9=11, so 11 is correct. The number 9 is only the constant term, not the first term, because the contribution of 2n must also be included when n=1. Exam tip: substitute n=1 in any nth-term formula to obtain the first term.
Frequently asked questions
What is the correct answer to this question?
11
Why is this the correct answer?
To find the first term, put n=1. Thus, a_1=2(1)+9=11, so 11 is correct. The number 9 is only the constant term, not the first term, because the contribution of 2n must also be included when n=1. Exam tip: substitute n=1 in any nth-term formula to obtain the first term.
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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