Question

27. The fifth and thirteenth terms of an arithmetic sequence are 5 and 77 , respectively. Find the first term and the tenth term.

Answer 1

if the first term is 13, the second will be 13+x, the third 13+2x and so on, the tenth term will be 13+9x=40 9x = 27 x = 3 so the difference between the terms is 3 the sum of the first 10 terms is 13*10 + (x+2x+…+9x) = 130 + 45x = 130 + 45*3 = 130 + 135 = 265

Explanation:

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