यदि किसी समांतर श्रेणी का (n)वाँ पद \(a_n=5n+4\) है, तो पहले (20) पदों का योग ज्ञात कीजिए।
If the (n)th term of an arithmetic progression is \(a_n=5n+4\), find the sum of the first (20) terms.
Explanation opens after your attempt
B. (1130)
Concept
The first term is (9) and the twentieth term is (104), so (S_{20}=\frac{20}{2}(9+104)=1130). Use \(a_n\) to find the first and last terms.
Why this answer is correct
The correct answer is B. (1130). The first term is (9) and the twentieth term is (104), so (S_{20}=\frac{20}{2}(9+104)=1130). Use \(a_n\) to find the first and last terms.
Exam Tip
पहला पद (9) और बीसवाँ पद (104) है, इसलिए (S_{20}=\frac{20}{2}(9+104)=1130)। \(a_n\) से पहले और अंतिम पद निकालें।
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