समांतर श्रेणी में \(a_8=45\) और \(a_{13}=80\) है। \(a_1\) क्या है?
In an arithmetic progression, \(a_8=45\) and \(a_{13}=80\). What is \(a_1\)?
Explanation opens after your attempt
A. (-4)
Concept
\(a_{13}-a_8=5d=35\), so (d=7) and (a_1=45-7(7)=-4). First find (d), then move backward.
Why this answer is correct
The correct answer is A. (-4). \(a_{13}-a_8=5d=35\), so (d=7) and (a_1=45-7(7)=-4). First find (d), then move backward.
Exam Tip
\(a_{13}-a_8=5d=35\), इसलिए (d=7) और (a_1=45-7(7)=-4)। पहले (d) निकालकर पीछे जाएं।
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