Số sánh√2017-√2018&√2018-√2019.
Đáp án: ta có√2017-√2018=1/√2017+√2018(1)
√2017-√2018=1/√2018+√2019(2)
Vì(1)>(2)nên√2017-√2018>√2018-√2019
Vậy √2017-√2018>√2018-√2019
Số sánh√2017-√2018&√2018-√2019. Đáp án: ta có√2017-√2018=1/√2017+√2018(1) √2017-√2018=1/√2018+√2019(2) Vì(1)>(2)nên√2017-√2
By Piper
Sai rồi bạn. PHải là
$\sqrt{2017} – \sqrt{2018} = \dfrac{2017-2018}{\sqrt{2017} + \sqrt{2018}} = \dfrac{-1}{\sqrt{2017} + \sqrt{2018}}$
Tương tự ta có
$\sqrt{2018} – \sqrt{2019} = \dfrac{-1}{\sqrt{2018} + \sqrt{2019}}$
Lại có
$\sqrt{2017} + \sqrt{2018} < \sqrt{2018} + \sqrt{2019}$
$<-> \dfrac{1}{\sqrt{2017} + \sqrt{2018}} > \dfrac{1}{\sqrt{2018} + \sqrt{2019}}$
$<-> \dfrac{-1}{\sqrt{2017} + \sqrt{2018}} < \dfrac{-1}{\sqrt{2018} + \sqrt{2019}}$
Do đó $\sqrt{2017} – \sqrt{2018} < \sqrt{2018} - \sqrt{2019}$