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Mathematics

If the first term of an A.P. is -5 and the common difference is 2, then the sum of its first 6 terms is

  1. 0

  2. 5

  3. 6

  4. 15

AP GP

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Answer

Given, a = -5 and d = 2.

We know that,

Sn=n2[2a+(n1)d]S6=62[2×5+(61)×2]=3[10+5×2]=3[10+10]=3×0=0.Sn = \dfrac{n}{2}[2a + (n - 1)d] \\[1em] \therefore S6 = \dfrac{6}{2}[2 \times -5 + (6 - 1) \times 2] \\[1em] = 3[-10 + 5 \times 2] \\[1em] = 3[-10 + 10] \\[1em] = 3 \times 0 \\[1em] = 0.

Hence, Option 1 is the correct option.

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