Đáp án:
` S = {2018} `
Lời giải chi tiết:
` \frac{2-x}{2016} - 1 = \frac{1-x}{2017} - \frac{x}{2018} `
` <=> \frac{2-x}{2016} - 1 + 2 = \frac{1-x}{2017} + 2 - \frac{x}{2018} `
` <=> \frac{2-x}{2016} + 1 = \frac{1-x}{2017} + 1 + 1 - \frac{x}{2018} `
` <=> \frac{2018-x}{2016} = \frac{2018-x}{2017} + \frac{2018-x}{2018} `
` <=> (2018 - x)(1/2016 - 1/2017 - 1/2018) = 0 `
` <=> 2018 - x = 0 `
` <=> x = 2018 `
Vậy ` S = {2018} `