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If (a_n=28-5n), what is the value of (a_7+a_{12})?
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Answer and explanation
Correct answer: -39
Given a_n=28-5n, a_7=28-5(7)=28-35=-7 and a_{12}=28-5(12)=28-60=-32. Therefore, a_7+a_{12}=-7+(-32)=-39. Option A can result from substituting an incorrect value of n in one of the terms. Exam tip: evaluate each required term separately before adding them.
Frequently asked questions
What is the correct answer to this question?
-39
Why is this the correct answer?
Given a_n=28-5n, a_7=28-5(7)=28-35=-7 and a_{12}=28-5(12)=28-60=-32. Therefore, a_7+a_{12}=-7+(-32)=-39. Option A can result from substituting an incorrect value of n in one of the terms. Exam tip: evaluate each required 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: nth term.
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