यदि \(a_3=7\) और \(a_{12}=61\) है, तो \(a_1\) क्या होगा?
If \(a_3=7\) and \(a_{12}=61\), what is \(a_1\)?
Explanation opens after your attempt
A. (-5)
Concept
\(a_{12}-a_3=9d=54\), so (d=6) and (a_1=7-2(6)=-5). Find the common difference first.
Why this answer is correct
The correct answer is A. (-5). \(a_{12}-a_3=9d=54\), so (d=6) and (a_1=7-2(6)=-5). Find the common difference first.
Exam Tip
\(a_{12}-a_3=9d=54\), इसलिए (d=6) और (a_1=7-2(6)=-5)। पहले समान अंतर निकालें।
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