найдите сумму всех целых чисел от -99 до 100 6 класс

Просто от 100 отнимаешь 99=1

-98,-97,-96,-95,-94,-93,-92,-91,-90,-89,-88,-87,-86,-85,-84,-83,-82,-81,-80,-79,-78,-77,-76,-75,-74,-73,-71,-70,-69,-68,-66,-65,-64,-63,-62,-61,-60,-59,-58,-57,-56,-55,-54,-54,-53,-52,-51,-50.