Find the sum of the following AP:-37, -33, -29,…, to 12 terms.

1.	Find the sum of the following AP:-37, -33, -29,…, to 12 terms.
Answer» Given A.P: -37, -33, -29,…, to 12 terms. a = -37; d = a₂ – a₁ = (-33) – (-37) = -33 + 37 = 4; n = 12 S_n = \(\frac{n}{2}\) [2a + (n – 1)d] ∴ S₁₂ = \(\frac{12}{2}\) [2 × (-37) + (12 – 1)4] = 6 [-74 + 11 × 4] = 6 [-74 + 44] = 6 × (-30) = -180

Answer»

Given A.P: -37, -33, -29,…, to 12 terms.

a = -37; d = a₂ – a₁ = (-33) – (-37) = -33 + 37 = 4; n = 12

S_n = \(\frac{n}{2}\) [2a + (n – 1)d]

∴ S₁₂ = \(\frac{12}{2}\) [2 × (-37) + (12 – 1)4]

= 6 [-74 + 11 × 4]

= 6 [-74 + 44]

= 6 × (-30)

= -180

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