Tìm x:

`  (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}` 

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}

-721

x . 17 = 51 

x        = 51 : 17 

x        =  3 

721 : x = 7 

        x = 721 : 7 

       x =    13 

chúc bạn học giỏi , k cho mình nha !

tìm x∈N biết 

x:17=51 

=> x = 51 x 17 

x = 867 

tìm x∈N biết  

721:x=7 

=> x = 721 : 7 

x = 103 

k nha bn

x:17=51

=>x=51:17

=>x=3

721:x=7

=>x=721:7

=>x=103

tíc mình nha

GJKFD;LGJJGRJ

Kết quả phép tính trên đâu mà bảo mình hộ bạn

`Answer:`

\(\frac{x+721}{2020}+\frac{x+21}{700}+\frac{x+721}{2021}=-1\) (Mình bổ sung đề nhé.)

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

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

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

Mà \(\frac{1}{2020}+\frac{1}{700}+\frac{1}{2021}\ne0\)

\(\Rightarrow x+721=0\Leftrightarrow x=-721\)

a: x=81-257=-176

b: x=-35+546=511

c: x=721+615=1336

d: x=-500:25=-20

e: x=-15*5=-75

f: x=612/9=68

1C

2A

1C        2A

giup vs mn oiiiii

\(\Leftrightarrow x^2-36-x^2+12x-9=9\)

\(\Leftrightarrow12x=54\)

hay x=9/2