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junior college 1 | H2 Maths

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Help is needed asap for part (ii), thanks in advance

So you can consider using substitutions like r = k + 1 which now makes the denominator (k) (k + 1) (k + 2).

But if r = k + 1, then r = 2 in the lower limit becomes k = 1 in be lower limit and N in the upper limit goes down by 1 as well to become N - 1.

This is equivalent to the original given expression in the question, except that we replace all N by N - 1.

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