A)  7/38 x 9/11 +7/38 x 4/11 -7/38 x 2/11

=7/38.(9/11+4/11-2/11)

=7/38

B) 5/31 x 21/25 + 5/31 x -7/10 - 5/31 x 9/20

=5/31.(21/25-7/10-9/20)

=5/31.(-31/100)

=-1/20

\(\frac{1}{3.5}+\frac{1}{5.7}+...+\frac{1}{x\left(x+2\right)}=\frac{11}{75}\)

\(\Leftrightarrow\frac{1}{2}\left(\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+...+\frac{1}{x}-\frac{1}{x+2}\right)=\frac{11}{75}\)

\(\Leftrightarrow\frac{1}{3}-\frac{1}{x+2}=\frac{11}{75}:\frac{1}{2}=\frac{22}{75}\Leftrightarrow\frac{1}{x+2}=\frac{1}{25}\Leftrightarrow x=23\)

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a) Ta có: \(3\left(x+5\right)-3=2\left(x+1\right)+7\)

\(\Leftrightarrow3x+15-3=2x+2+7\)

\(\Leftrightarrow3x+12=2x+9\)

hay x=-3

b) Ta có: \(15-\left(x+2\right)^2=-1\)

\(\Leftrightarrow\left(x+2\right)^2=16\)

\(\Leftrightarrow\left[{}\begin{matrix}x+2=4\\x+2=-4\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=2\\x=-6\end{matrix}\right.\)

c) Ta có: \(75-\left(2x+1\right)^3=11\)

\(\Leftrightarrow\left(2x+1\right)^3=64\)

\(\Leftrightarrow2x+1=4\)

hay \(x=\dfrac{3}{2}\)

a) Ta có: $3\left(x+5\right)-3=2\left(x+1\right)+7$

$\iff 3x+15-3=2x+2+7$

$\iff 3x+12=2x+9$

hay x=-3

b) Ta có: $15-{}^{}=-1$

$\iff {}^{}=16$

⇔[x+2=4x+2=−4⇔[x=2x=−6⇔[x+2=4x+2=−4⇔[x=2x=−6

c) Ta có: $75-{}^{}$

`3(x+5)-3=2(x+1)+7`

`3x+15-3=2x+2+7`

`x=-3`

.

`15-(x+2)^2=-1`

`(x+2)^2=16`

`(x+2)^2=4^2=(-4)^2`

`[(x+2=4),(x+2=-4):}`

`[(x=2),(x=-6):}`

.

`75-(2x+1)^3=11`

`(2x+1)^3=64`

`(2x+1)^2=4^3`

`2x+1=4`

`x=3/2`

$3(x+5)-3=2(x+1)+7$

$3x+15-3=2x+2+7$

$x=-3$

.

$15-{}^{}=-1$

${}^{}=16$

${}^{}={}^{}={}^{}$

$[\begin{array}{c}x+2=4\\ x+2=-4\end{array}$

$[\begin{array}{c}x=2\\ x=-6\end{array}$

a) Ta có: \(3\left(x+5\right)-3=2\left(x+1\right)+7\)

\(\Leftrightarrow3x-2x=2+7-15+3\)

hay x=-3

b) Ta có: \(15-\left(x+2\right)^2=-1\)

\(\Leftrightarrow\left(x+2\right)^2=16\)

\(\Leftrightarrow\left[{}\begin{matrix}x+2=4\\x+2=-4\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=2\\x=-6\end{matrix}\right.\)

hơi khó anh mai ơi !

hơi bị khó... chờ mình ghi lại để hỏi cô!!!

dấu này"/" là chia hay phần

A = ( 4/4 + 2/3 ) - ( 51/3 - 6/5 ) - ( 6 - 7/4 + 3/2 )

Sau đó quy đồng rồi trừ cả là đc 

B tương tự 

C=13/15 

D cx thế . Bạn tự vận dụng đi . Xl vì ko giải đc . Mik đang gấp

1:

a: =8/7-5/88=669/616

b: \(=1+\dfrac{2}{9}\cdot\dfrac{3}{7}-\dfrac{10}{7}=1+\dfrac{2}{21}-\dfrac{10}{7}\)

\(=\dfrac{21+2-30}{21}=\dfrac{-7}{21}=\dfrac{-1}{3}\)

c: \(=\dfrac{11}{3}-\dfrac{6}{7}+4=\dfrac{77-18+84}{21}=\dfrac{143}{21}\)

Bài 2:

a: =>9/4-x=5/11*2=10/11

=>x=9/4-10/11=59/44

b: =>2/9:x=19/21

=>x=2/9:19/21=14/57