A) \[^{15}{{C}_{5}}\]
B) \[^{15}{{C}_{6}}\]
C) \[^{15}{{C}_{4}}\]
D) \[^{15}{{C}_{7}}\]
Correct Answer: C
Solution :
Let \[{{T}_{r+1}}\] term containing x32. Therefore \[^{15}{{C}_{r}}{{x}^{4r}}{{\left( \frac{-1}{{{x}^{3}}} \right)}^{15-r}}\] Þ \[{{x}^{4r}}{{x}^{-45+3r}}={{x}^{32}}\Rightarrow 7r=77\Rightarrow r=11\]. Hence coefficient of x32 is \[^{15}{{C}_{11}}\] or \[^{15}{{C}_{4}}\]You need to login to perform this action.
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