Question

Вычислите без калькулятора: 1 + 2 – 3 – 4 + 5 + 6 – 7 – 8 + … –2016 + 2017.

Answer 1

Сгруппируем так
(1-3) + (2-4) + (5-7) + (6-8) + ... + (2013-2015) + (2014-2016) + 2017 =
= (-2) + (-2) + ... + (-2) + (-2) + 2017 = -2*2016/2 + 2017 = -2016 + 2017 = 1