यदि \(a_1=80\) और (a_{n+1}=a_n-\frac{n(n+1)}{2}-1) है तो \(a_4\) क्या होगा?
If \(a_1=80\) and (a_{n+1}=a_n-\frac{n(n+1)}{2}-1), what is \(a_4\)?
Explanation opens after your attempt
Correct Answer
A. (69)
Concept
The terms are (80,78,74,67), so \(a_4=67\). Exam tip: the subtractions are (2,4,7) in order.
Why this answer is correct
The correct answer is A. (69). The terms are (80,78,74,67), so \(a_4=67\). Exam tip: the subtractions are (2,4,7) in order.
Exam Tip
पद (80,78,74,67) नहीं बल्कि \(a_4=67\) है। घटाव (2,4,7) क्रम से होता है।
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