यदि (^{n}P_r=\frac{n!}{(n-r)!}) है तो \(^{n}P_{r-1}\) किसके बराबर होगा?
If (^{n}P_r=\frac{n!}{(n-r)!}) then what is \(^{n}P_{r-1}\)?
Explanation opens after your attempt
Correct Answer
A. (\frac{n!}{(n-r+1)!})
Concept
Putting (r-1) makes the denominator ((n-r+1)!). In exams watch signs carefully while substituting.
Why this answer is correct
The correct answer is A. (\frac{n!}{(n-r+1)!}). Putting (r-1) makes the denominator ((n-r+1)!). In exams watch signs carefully while substituting.
Exam Tip
(r-1) रखने पर हर ((n-r+1)!) बनता है। परीक्षा में substitution करते समय signs ध्यान से देखें।
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