Будьласка!!!!! Срочно допоможіть!!!!!! Даю 50 балів, тільки зробіть правильно!! Завдання на тему: АРИФМЕТИЧНА ПРОГРЕСІЯ. Зробити номер 727:

Ответ

Автор - mshatun

$a_{1} = 1.5 : : d = x : : a_{n} = 54 : : s_{n} = 999 \ s_{n} = frac{a_{1} + a_{n}}{2} times n = 999 \ frac{1.5 + 54}{2} times n = 999 \ 27.75n = 999 \ n = 36 \ \ a_{36} = a_{1} + 35d = 54 \ 1.5 + 35d = 54 \ 35d = 52.5 \ d = 1.5$

$a_{1} = 0.2 : : d = x : : a_{n} = 5.2 : : s_{n} = 137.7 \ s_{n} = frac{a_{1} + a_{n}}{2} times n =137.7 \ frac{0.2 + 5.2}{2} times n = 137.7 \ 2.7n = 137.7 \ n = 51 \ \ a_{51} = a_{1} + 50d = 5.2 \ 0.2 + 50d = 5.2 \ 50d = 5 \ d = 0.1$

$a_{1} = - 28 : : d = x : : n = 9 : : a_{n} = y : : s_{9} = 0 \ s_{9} = frac{a_{1} + a_{9} }{2} times 9 = 0 \ frac{ - 28 + a_{9}}{2} times 9 = 0 \ (- 28 + a_{9}) times 18 = 0 \ a_{9} = 28 \ a_{9} = a_{1} + 8d = 28 \ - 28 + 8d = 28 \ 8d = 56 \ d = 7$

$a_{1} = 0.7 : : d = x : : n = 30 : : a_{n} = y : : s_{30} = 108 \ s _{30} = frac{a_{1} + a_{30}}{2} times 30 = 108 \ frac{0.7 + a_{30} }{2} times 30 = 108 \ (0.7 + a_{30}) times 60 = 216 \ 0.7 + a_{30} = 3.6 \a_{30} = 2.9 \ \ a_{30} =a_{1} + 29d = 2.9 \ 0.7 + 29d = 2.9 \ 29d = 2.2 \ d = 0.07586$

$a_{1} = x : : d = y : : n = 14 : : a_{14} = 140 : : s_{14} = 1050 \ s_{14} = frac{a_{1} + a_{14}}{2} times 14 = 1050 \ frac{a_{1} + 140}{2} times 14 = 1050 \ (a_{1} + 140) times 28 = 2100 \ a_{1} + 140 = 75 \ a_{1} = - 65 \ \ a_{14} = a_{1} + 13d = 140 \ - 65 + 13d = 140 \ 13d = 205 \ d = 15.8$

$a_{1} = x : : d = y : : n = 10 : : a_{10} = - 37 : : s_{10} = - 55 \ s_{10} = frac{a_{1} + a_{10}}{2} times 10 = - 55 \ (a_{1} - 37) times 20 = - 110 \ a_{1} - 37 = - 5.5 \ a_{1} = 31.5 \ \ a_{10} = a_{1} + 9d = - 37 \ 31.5 + 9d = - 37 \ 9d = - 68.5 \ d = 7.6$

$a_{1} = x : : d = 3 : : n = 31 : : a_{31} = y : : s_{31} = 0 \ s_{31} = frac{2a_{1} + 30d}{2} times 31 = 0 \ (a_{1} + 45) times 31 = 0 \ a_{1} = - 45 \ \ a_{31} = a_{1} + 30d = - 45 + 90 = 45$

$a_{1} = x : : d = frac{1}{3} : : n = 37 : : a_{37} = y : : s_{37} = 209 frac{2}{3} \ s_{37} = frac{2a_{1} + 36d}{2} times 37 = 209 frac{2}{3} \ (a_{1} + 18d) times 37 = 209 frac{2}{3} = frac{629}{3} \ a_{1} + 6 = frac{17}{3} \ a_{1} = - frac{1}{3} \ \ a_{37} = a_{1} + 36d = - frac{1}{3} + 12 = frac{35}{3} = 11 frac{2}{3}$

сколько смогла