Арифметическое прогрессия

Question

Арифметическое прогрессия

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Answer 1

C1 = 4
c2 = c1 + 2 = 6
d = c2 - a1 = 6 - 4 = 2

c12 = c1 + 11d = 4 + 11*2 = 22 + 4 = 26