以下方程为等差数列 aia, start subscript, i, end subscript:
a1=2a, start subscript, 1, end subscript, equals, 2 ai=ai−1−3a, start subscript, i, end subscript, equals, a, start subscript, i, minus, 1, end subscript, minus, 3
算出 −50+(−44)+(−38)+...+2038+2044minus, 50, plus, left parenthesis, minus, 44, right parenthesis, plus, left parenthesis, minus, 38, right parenthesis, plus, point, point, point, plus, 2038, plus, 2044 之和.