Some Special Series — MATHS STD 11 Science — Question
Rajasthan BoardEnglish MediumSTD 11 ScienceMATHSSome Special Series1 Mark
Question
Write the sum of the series 2 + 4 + 6 + 8 + ... + 2n.
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Answer
Let Tn be the term of the given series and Sn be the sum of the given series. $\therefore\ \text{T}_\text{n}=2\text{n}$ $\therefore\ \text{S}_\text{n}=\sum\limits^{\text{n}}_{\text{k}=1}\text{T}_\text{k}=\sum\limits^{\text{n}}_{\text{k}=1}2\text{k}$ $=2\sum\limits^{\text{n}}_{\text{k}=1}\text{k}$ $=2\Big[\frac{\text{n}(\text{n}+1)}{2}\Big]$ $=\text{n}(\text{n}+1)$ Hence, $\text{S}_\text{n}=\text{n}(\text{n}+1)$
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