\(\sum_{r=0}^{n}{}^{n}C_r{}^{r}C_3\) को किस रूप में लिखा जाएगा?
In which form is \(\sum_{r=0}^{n}{}^{n}C_r{}^{r}C_3\) written?
Explanation opens after your attempt
B. \(^{n}C_3 2^{n-3}\)
Concept
Choose the (3) marked members first and let each of the remaining (n-3) members enter the subset or not. In exams count the inner selection first.
Why this answer is correct
The correct answer is B. \(^{n}C_3 2^{n-3}\). Choose the (3) marked members first and let each of the remaining (n-3) members enter the subset or not. In exams count the inner selection first.
Exam Tip
पहले (3) चिह्नित सदस्य चुनें और बाकी (n-3) सदस्य subset में आएं या न आएं। परीक्षा में अंदर वाले चयन को पहले गिनना तेज होता है।
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