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Arithmetic Progressions

RD Sharma

CBSE

Grade 10

Question:

If the sum of $n$ terms of an A.P. is $S_n = 3n^2 - n$, then the first term is:
(a) $2$
(b) $3$
(c) $1$
(d) $4$

Step-by-Step Solution

Key Concept: $a_1 = S_1 = 3(1)^2 - 1 = 2$.

$S_1 = 3(1) - 1 = 2$. [1.0 Mark]

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🎯 Official CBSE Marking Scheme:
Evaluating $S_1 = 2$: 1.0 Mark

Correct Answer: $2$

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