Đáp án:
`ĐK : x > 2019 ; y > 2020 ; z > 2021`
`(1 - \sqrt{x - 2019})/(x - 2019) + (1 - \sqrt{y - 2020})/(y - 2020) + (1 - \sqrt{z - 2021})/(z - 2021) + 3/4 =0`
`↔ 1/(x - 2019) - 2 . 1/(\sqrt{x - 2019}) . 1/2 + 1/4 + 1/(y - 2020) - 2 . 1/(\sqrt{y - 2020}) . 1/2 + 1/4 + 1/(z - 2021) - 2. 1/(\sqrt{z - 2021}) . 1/2 + 1/4 = 0`
`↔ (1/(\sqrt{x - 2019}) - 1/2)^2 + (1/(\sqrt{y - 2020}) - 1/2)^2 + (1/(\sqrt{z - 2021}) - 1/2)^2 = 0`
`↔ 1/(\sqrt{x - 2019}) - 1/2 = 1/(\sqrt{y - 2020}) - 1/2 = 1/(\sqrt{z - 2021}) - 1/2 = 0`
`↔ 1/(\sqrt{x - 2019}) = 1/(\sqrt{y - 2020}) = 1/(\sqrt{z - 2021}) = 1/2`
`↔ \sqrt{x - 2019} = \sqrt{y - 2020} = \sqrt{z - 2021} = 2`
`↔ x - 2019 = y - 2020 = z - 2021 = 4`
`↔ x = 2023 ; y = 2024 ; z = 2025`
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