समांतर श्रेणी \(15,21,27,33,\ldots\) में \(a_n=87\) के लिए (n) क्या है?
In the arithmetic progression \(15,21,27,33,\ldots\), what is (n) for \(a_n=87\)?
Explanation opens after your attempt
C. (13)
Concept
(a_n=15+(n-1)6=6n+9), so (6n+9=87) gives (n=13). Form the general term and solve the equation.
Why this answer is correct
The correct answer is C. (13). (a_n=15+(n-1)6=6n+9), so (6n+9=87) gives (n=13). Form the general term and solve the equation.
Exam Tip
(a_n=15+(n-1)6=6n+9), इसलिए (6n+9=87) से (n=13)। सामान्य पद बनाकर समीकरण हल करें।
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