यदि \(\frac{^{n}C_4}{^{n}C_3}=2\) हो, तो कौन-सा समीकरण सही बनेगा?
If \(\frac{^{n}C_4}{^{n}C_3}=2\), which equation is formed correctly?
Explanation opens after your attempt
B. \(n-3=2\times4\)
Concept
The ratio is \(\frac{^{n}C_r}{^{n}C_{r-1}}=\frac{n-r+1}{r}\), so for (r=4), \(\frac{n-3}{4}=2\). In exams use the ratio formula for adjacent combinations.
Why this answer is correct
The correct answer is B. \(n-3=2\times4\). The ratio is \(\frac{^{n}C_r}{^{n}C_{r-1}}=\frac{n-r+1}{r}\), so for (r=4), \(\frac{n-3}{4}=2\). In exams use the ratio formula for adjacent combinations.
Exam Tip
अनुपात \(\frac{^{n}C_r}{^{n}C_{r-1}}=\frac{n-r+1}{r}\) है, इसलिए (r=4) पर \(\frac{n-3}{4}=2\) मिलेगा। परीक्षा में adjacent combinations में ratio formula लगाएँ।
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