Permutations And Combinations Question 159
Question: $ ^{n-1}C _{r}=(k^{2}-3).{{}^{n}}{C _{r+1}} $ if $ k\in $ [IIT Screening 2004]
Options:
A) $ [-\sqrt{3},\sqrt{3}] $
B) $ (-\infty ,-2) $
C) $ (2,\infty ) $
D) $ (\sqrt{3},2) $
Correct Answer: D $ \Rightarrow $ $ k^{2}=\frac{r+1}{n}+3,\frac{1}{n}\le \frac{r+1}{n}\le 1 $
Þ $ k^{2}\in [ \frac{1}{n}+3,4 ],n\ge 2 $ $ k\in [ -2,-\sqrt{\frac{1}{n}+3} ]\cup [ \sqrt{\frac{1}{n}+3},2 ];n\ge 2 $ .
Show Answer
Answer:
Solution:
BETA
