1)10/21

2)2/3

3)63/2

\(-\dfrac{4}{7}-x=\dfrac{3}{5}-2x\\ \Rightarrow-x+2x=\dfrac{3}{5}+\dfrac{4}{7}\\ \Rightarrow x=\dfrac{21}{35}+\dfrac{20}{35}\\ \Rightarrow x=\dfrac{41}{35}\)

Vậy `x=41/35`

__

\(\dfrac{3}{7}x-\dfrac{2}{3}x=\dfrac{10}{21}\\ \Rightarrow\left(\dfrac{3}{7}-\dfrac{2}{3}\right)x=\dfrac{10}{21}\\ \Rightarrow\left(\dfrac{9}{21}-\dfrac{14}{21}\right)x=\dfrac{10}{21}\\ \Rightarrow\dfrac{-5}{21}x=\dfrac{10}{21}\\ \Rightarrow x=\dfrac{10}{21}:\left(-\dfrac{5}{21}\right)\\ \Rightarrow x=-2\)

Vậy `x=-2`

a)

-4/7 - x = 3/5 - 2x

2x - x = 3/5 + 4/7

x = 41/35

Vậy x = 41/35

b)

3/7.x - 2/3.x = 10/21

x(3/7 - 2/3) = 10/21

x.(-5/21) = 10/21

x = 10/21 : (-5/21) = -2

Vậy x = -2

\(\frac{-8}{3}+\frac{-1}{3}\)=\(\frac{-9}{3}\)

=-3

\(\frac{-2}{7}+\frac{-1}{7}=\frac{-3}{7}< 0\)

Đề bài trở thành:-3<x<0

Vậy các số cần tìm là -2;-1

lát mình giải tiếp nha

Ý 2 quy đồng mẫu số là 168 rổi khử mẫu đi.Sau đó thì tự giải

Ý 3 quy đồng mẫu số là 120 rổi khử mẫu đi.Sau đó thì tự giải

=>Không rỗi hơi quy đồng mẫu lớn thế đâu

a: =30-22=8

b: =10*(23+17)=10*40=400

c: =21*3-7*(-14)

=63+98=161

d: =-20-[10*10*5^2+16]

=-20-100*25-16

=-36-2500

=-2536

`3/7 x -2/3 x =10/21`

`=> (3/7-2/3)x=10/21`

`=> ( 9/21 - 14/21)x=10/21`

`=>-5/21 x=10/21`

`=> x=10/21 : (-5/21)`

`=> x=10/21 xx (-21/5)`

`=>x=-2`

(3/7 - 2/3).x = 10/21

-5/21.x = 10/21

x = 10/21 : (-5/21) 

x = -2

vậy x = -2

a) 2/3 x + 1/2 = 1/10

2/3 x = 1/10 - 1/2

2/3 x = -2/5

x = -2/5 : 2/3

x = -3/5

b) 2/3 x + 1/5 = 7/10

2/3 x = 7/10 - 1/5

2/3 x = 1/2

x = 1/2 : 2/3

x = 3/4

c) (3 4/5 - 2x) . 1 1/3 = 5

19/5 - 2x = 5 : 4/3

19/5 - 2x = 15/4

2x = 19/5 - 15/4

2x = 1/20

x = 1/20 : 2

x = 1/40

d) x/7 = 6/(-21)

x = 6.7/(-21)

x = -2

Tính:

\(\dfrac{10}{21}-1\cdot251+\dfrac{11}{21}+2\cdot251\\ 251\cdot\left(\dfrac{10}{21}+\dfrac{11}{21}\right)+\left(2-1\right)\\ 251\cdot1+1=252\)

Tìm x

c,\(\left(3x-1\right)^2:7=7\\ \left(3x-1\right)^2=7\cdot7=14\\ \left(3x-1\right)^2=\left(\pm7\right)^2\\ \Rightarrow\left[{}\begin{matrix}3x-1=7\\3x-1=-7\end{matrix}\right.\\ \Rightarrow\left[{}\begin{matrix}3x=7+1=8\\3x=-7+1=-6\end{matrix}\right.\\ \Rightarrow\left[{}\begin{matrix}x=\dfrac{8}{3}\\x=-\dfrac{6}{3}=-2\end{matrix}\right.\)

Vậy x={8/3;-2}

d; \(\left(7-2x\right)^3=\left(\dfrac{1}{2}\right)^2\cdot\left(-\dfrac{1}{2}\right)\\ \left(7-2x\right)^3=\left(-\dfrac{1}{2}\right)^3\\ 7-2x=-\dfrac{1}{2}\\ 2x=7--\dfrac{1}{2}=\dfrac{15}{2}\\ x=\dfrac{15}{2}:2=\dfrac{15}{4}\)

giúp với mn ơiii

A = \(\dfrac{10}{21}\) - 1.251 + \(\dfrac{11}{21}\) + 2.251

A = (\(\dfrac{10}{21}\) + \(\dfrac{11}{21}\)) - 1.251 + 2.251

A = \(\dfrac{21}{21}\) + 251

A = 1 + 251

A = 252

C, (3\(x\) - 1)²: 7 = 7

     (3\(x\) -1)²     = 7 x  7

     (3\(x\) -1)² = 49

    \(\left[{}\begin{matrix}3x-1=7\\3x-1=-7\end{matrix}\right.\)

    \(\left[{}\begin{matrix}3x=8\\3x=-6\end{matrix}\right.\)

   \(\left[{}\begin{matrix}x=\dfrac{8}{3}\\x=-2\end{matrix}\right.\)

Vậy \(x\) \(\in\){-2;\(\dfrac{8}{3}\)}

d, (7 - 2\(x\))³ = (\(\dfrac{1}{2}\))² \(\times\) (- \(\dfrac{1}{2}\))

    (7- 2\(x\))³ =  (- \(\dfrac{1}{2}\))³

    7 - 2\(x\)   = - \(\dfrac{1}{2}\)

       2\(x\)     = 7 + \(\dfrac{1}{2}\)

       2\(x\)     = \(\dfrac{15}{2}\)

          \(x\)     = \(\dfrac{15}{2}\): 2

         \(x\)     =   \(\dfrac{15}{4}\)

a: \(=\dfrac{3}{5}:\dfrac{7}{5}=\dfrac{3}{5}\cdot\dfrac{5}{7}=\dfrac{3}{7}\)

b: \(=\dfrac{9}{17}\left(\dfrac{8}{5}-\dfrac{3}{5}\right)+\dfrac{8}{17}\)

=9/17+8/17=1

c: =>x-3/10=7/15*1/5=7/75

=>x=7/75+3/10=59/150