6. An arithmetic series has sixth term 28 and tenth term 44.
a) Find the first term and the common difference.
U6 = a + (6-1)d, 28 = a +5d---(1)
U10 = a + (10-1)d, 44 = a + 9d---(2)
(1) - (2)
16 = 4d
d = 4
a = 15 - 5 * 4
a = 8
b.Find the sum of the first terms of the series.
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