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Question : 34 of 160
Marks:
+1,
-0
Solution:
1×1!+2×2!+...+n×n! =(2−1)×1!+(3−1)×2!+...+[(n+1)−1]×n!
={2×1!+3×2!+4×3!+...(n+1)×n!}
−{1×1!+1×2!+1×3!+...+1×n!}
=(n+1)!−1!=11!−1! (given)
So,
n=10 Now, maximum value of
‌10Cr occurs when
r=‌=‌=5 Now,
‌10C5=‌=252
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