Tìm x, biết: x+721/2020 + x+21/700 + x+721/2021 = -1.
[tex]\frac{x+721}{2020} + \frac{x+21}{700} + \frac{x+721}{2021} = -1[/tex]
[tex]\Leftrightarrow \frac{x+721}{2020} + \frac{x+21}{700}+1 + \frac{x+721}{2021} = 0[/tex]
[tex]\Leftrightarrow \frac{x+721}{2020} + \frac{x+721}{700} + \frac{x+721}{2021} =0[/tex]
[tex]\Leftrightarrow (x+721)(\frac{1}{2020} + \frac{1}{700}+ \frac{1}{2021} )=0[/tex]
[tex]\Rightarrow x=-721[/tex]