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Tim Gan Math

2006 A-Level H2 Mathematics

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Question 3Sequence and Series5 marks

Verify that if

\({{v}_{n}}=n\left( n+1 \right)\left( n+2 \right)...\left( n+m \right)\).

then

\({{v}_{n+1}}-{{v}_{n}}=\left( m+1 \right)\left( n+1 \right)\left( n+2 \right)...\left( n+m \right)\).[2]

Given now that

\({{u}_{n}}=\left( n+1 \right)\left( n+2 \right)...\left( n+m \right)\),

find \(\sum\limits_{n=1}^{N}{{{u}_{n}}}\) in terms of \(m\) and \(N\).[3]

Final Answer:

${\frac{1}{m+1}[(N+1)(N+2)(N+3)...(N+1+m)-(1)(2)(3)...(m+1)]}$