Arrange 1, - 1 / 2, 1 / 3, - 1 / 4, 1 / 5, - 1 / 6 according to certain rules in the following table First line 1 Second line - 1 / 2 1 / 3 The third line - 1 / 4 1 / 5 - 1 / 6 .. The seventh number from left to right in line 199 is () please give me some ideas

Arrange 1, - 1 / 2, 1 / 3, - 1 / 4, 1 / 5, - 1 / 6 according to certain rules in the following table First line 1 Second line - 1 / 2 1 / 3 The third line - 1 / 4 1 / 5 - 1 / 6 .. The seventh number from left to right in line 199 is () please give me some ideas

The denominator of the last number in line 198 is [198 * (1 + 198)] / 2 = 19701, that is, the last number in line 198 is 1 / 19701. The formula used is equal ratio summation formula Sn = [n * (a1 + an)] / 2
So the number of line 199 is - 1 / 19702 1 / 19703 - 1 / 19704 1 / 19705 - 1 / 19706 1 / 19707 - 1 / 19708
So the seventh number from left to right is (- 1 / 19708)