Найдите первый член и разность арифметической прогрессиисn,если:1)с5=27,с27=60.2)с20=0,с66=-92.

c(n) = c(1) + (n - 1)d.

1) c(5) = c(1) + 4d = 27,

c(27) = c(1) + 26d = 60;

26d - 4d = 60 - 27;

22d = 33;

d = 33 / 22 = 3/2;

c(1) = 27 - 4 3/2 = 27 - 6 = 21.

2) c(20) = c(1) + 19d = 0,

c(66) = c(1) + 65d = -92;

65d - 19d = -92 - 0;

46d = -92;

d = -92 / 46 = -2;

c(1) = 0 - 19 (-2) = 38.