(n) distinct symbols से length (r) strings में exactly one repeated symbol और बाकी all distinct हों, तो count का core expression क्या होगा?
Explanation opens after your attempt
A. \(n\cdot{}^{n-1}C_{r-2}\cdot\frac{r!}{2!}\)
Concept
Choose the repeated symbol, choose the remaining (r-2) distinct symbols, then arrange the multiset. In exams fix the repeated item first for exactly one repeat.
Why this answer is correct
The correct answer is A. \(n\cdot{}^{n-1}C_{r-2}\cdot\frac{r!}{2!}\). Choose the repeated symbol, choose the remaining (r-2) distinct symbols, then arrange the multiset. In exams fix the repeated item first for exactly one repeat.
Exam Tip
Repeated symbol चुनें, बाकी (r-2) distinct symbols चुनें, फिर multiset arrange करें। परीक्षा में exactly one repeat में repeated item पहले fix करें।
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