Question

Tìm x :

\(\dfrac{x+721}{2020}\) + \(\dfrac{x+21}{700}\) + \(\dfrac{x+721}{2021}\) = -1

Answer 1

`  (x+721) /2020+(x+21) /700+ (x+721)/2021=-1`

`<=>(x+721)/2020+(x+21) /700+ 1+ (x+721)/2021=0`

`<=>(x+721)/2020+(x+721) /700+ (x+721)/2021=0 `

`<=>(x +721) (1/2020+1/700+1/2021 )= 0` 

Vì `1/2020+1/700+1/2021>0` 

 `=>x+721 =0 <=>x=-721`

Vậy `S={-721}` 

Answer 2

Ta có: \(\dfrac{x+721}{2020}+\dfrac{x+21}{700}+\dfrac{x+721}{2021}=-1\)

\(\Leftrightarrow\dfrac{x+721}{2020}+\dfrac{x+721}{700}+\dfrac{x+721}{2021}=0\)

\(\Leftrightarrow\left(x+721\right)\left(\dfrac{1}{2020}+\dfrac{1}{700}+\dfrac{1}{2021}\right)=0\)

mà \(\dfrac{1}{2020}+\dfrac{1}{700}+\dfrac{1}{2021}>0\)

nên x+721=0

hay x=-721

Vậy: S={-721}

Answer 3

-721

Answer 4

\(\frac{x+721}{2020}+\frac{x+21}{700}+\frac{x+721}{2021}=-1\)

\(\Leftrightarrow\frac{x+721}{2020}+\frac{x+21}{700}+1+\frac{x+721}{2021}=0\)

\(\Leftrightarrow\frac{x+721}{2020}+\frac{x+21}{700}+\frac{x+721}{2021}=0\)

\(\Leftrightarrow\left(x+721\right)\left(\frac{1}{2020}+\frac{1}{700}+\frac{1}{2021}\right)=0\)

\(\text{Vì }\frac{x+721}{2020}+\frac{x+21}{700}+\frac{x+721}{2021}>0\)

\(\Rightarrow x+721=0\)

     \(x\)            \(=0-721=-721\)