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Given a=7,a13=35 find d and S13 |
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Answer» a = 7 A13 = 35 a13 = a + 12d = 35 7 + 12d = 35 d = 28 / 12 = 7 / 3 S13 = n/2 (a + a13) = 13/2 (7 + 35) = 13 * 21 S13 = 273 |
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