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Question
If\[\ ^{( a^2 - a)}{}{C}_2 = \ ^{( a^2 - a)}{}{C}_4\] , then a =
Options
2
3
4
none of these
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Solution
3
\[ \Rightarrow a^2 - 3a + 2a - 6 = 0\]
\[ \Rightarrow a \left( a - 3 \right) + 2 \left( a - 3 \right) = 0\]
\[ \Rightarrow \left( a + 2 \right) \left( a - 3 \right) = 0\]
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