The expression C0+2C1+3C2+......+(n+1)Cn is equal to
A
2n−1
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B
n(2n−1)
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C
n(2n−1)+2n
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D
(n+1)2n
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Solution
The correct option is An(2n−1)+2n Let E=C0+2C1+3C2+......nCn−1+(n+1)Cn........(1) Using Cr=Cn−rE=(n+1)C0+nC1+(n−1)C2+.....+2Cn−1+Cn........(2) Adding (1) and (2), we get 2E=(n+2)C0+(n+2)C1+(n+2)C2+....+(n+2)Cn =(n+2){C0+C1+.....+Cn}=(n+2)2n ⇒E=(n+2)2n−1