Sn denote the sum of the first n terms of an a.p prove that S12=3(S8-S

1.	Sn denote the sum of the first n terms of an a.p prove that S12=3(S8-S4)
Answer» So easy......S12 = n/2 ( 2a + (n - 1)d )S12 = 12/2 ( 2a + (12 - 1)d )S12 = 6 (2a + 11d)S12 = 12a + 66dSimilarly , we find value of S8 and S4S8 = 8a + 28dS4 = 4a + 6d3(S8 - S4)3( 8a + 28d - 4a - 6d)3( 4a + 22d)12a + 66d12a + 66d = S12S12 = 3(S8 - S4)Hence , proved.???

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