a, \(\left(x-2\right)^3=-27\)

\(\Rightarrow\left(x-2\right)^3=-3^3\)

\(\Rightarrow x-2=-3\)

\(\Rightarrow x=-3+2=-1\)

b, \(\left|3,5-x\right|+\dfrac{2}{7}=\dfrac{16}{7}\)

\(\Rightarrow\left|3,5-x\right|=\dfrac{16}{7}-\dfrac{2}{7}=\dfrac{14}{7}=2\)

\(\Rightarrow\left[{}\begin{matrix}3,5-x=2\\3,5-x=-2\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=1,5\\x=5,5\end{matrix}\right.\)

\(\left(x-2\right)^3=-27\)
\(\left(x-2\right)^3=-3^3\)
=> \(x-2=-3\)
\(x=-3+\left(-2\right)\)
\(x=-5\)
Vậy x=5

\(\left|3,5-x\right|+\dfrac{2}{7}=\dfrac{16}{7}\)
\(\left|3,5-x\right|=\dfrac{16}{7}-\dfrac{2}{7}\)
\(\left|3,5-x\right|=\dfrac{14}{7}\)
\(\left|3,5-x\right|=2\)
=> \(3,5-x=2hoặc3,5-x=-2\)
\(x=3,5-2\) hoặc \(x=3,5-\left(-2\right)\)
\(x=1,5\) hoặc \(x=3,5+2\)
\(x=1,5\) hoặc \(x=5,5\)
Vậy x=1,5 hoặc x=5,5

\(a)\left(x-2\right)^3=-27\)

\(\Rightarrow\left(x-2\right)^3=-3^3\)

\(\Rightarrow x-2=-3\)

\(\Rightarrow x=-3+2=-1\)

\(b)\left|3,5-x\right|+\dfrac{2}{7}=\dfrac{16}{7}\)

\(\Rightarrow\left|3,5-x\right|=\dfrac{16}{7}-\dfrac{2}{7}\)

\(\Rightarrow\left|3,5-x\right|=2\)

\(\Rightarrow\left[{}\begin{matrix}3,5-x=2\\3,5-x=-2\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=1,5\\x=5,5\end{matrix}\right.\)

Chúc bạn học tốt!

1:

a: =7/5(40+1/4-25-1/4)-1/2021

=21-1/2021=42440/2021

b: =5/9*9-1*16/25=5-16/25=109/25

a: =>x-3/4=1/6-1/2=1/6-3/6=-2/6=-1/3

=>x=-1/3+3/4=-4/12+9/12=5/12

b: =>x(1/2-5/6)=7/2

=>-1/3x=7/2

hay x=-21/2

c: (4-x)(3x+5)=0

=>4-x=0 hoặc 3x+5=0

=>x=4 hoặc x=-5/3

d: x/16=50/32

=>x/16=25/16

hay x=25

e: =>2x-3=-1/4-3/2=-1/4-6/4=-7/4

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

hay x=5/8

\(\dfrac{x}{x+2}+\dfrac{7x-16}{\left(x+2\right)\left(4x-7\right)}\left(dkxd:x\ne-2;x\ne\dfrac{7}{4}\right)\)

\(=\dfrac{x\left(4x-7\right)+7x-16}{\left(x+2\right)\left(4x-7\right)}\)

\(=\dfrac{4x^2-7x+7x-16}{\left(x+2\right)\left(4x-7\right)}\)

\(=\dfrac{4x^2-16}{\left(x+2\right)\left(4x-7\right)}\)

\(=\dfrac{4\left(x^2-4\right)}{\left(x+2\right)\left(4x-7\right)}\)

\(=\dfrac{4\left(x-2\right)\left(x+2\right)}{\left(x+2\right)\left(4x-7\right)}\)

\(=\dfrac{4\left(x-2\right)}{4x-7}\)

\(=\dfrac{4x-8}{4x-7}\)

===============================

\(\dfrac{x}{x-2}+\dfrac{2}{2-x}\left(dkxd:x\ne2\right)\)

\(=\dfrac{x}{x-2}-\dfrac{2}{x-2}\)

\(=\dfrac{x-2}{x-2}\)

\(=1\)

\(\left(\dfrac{7}{8}-\dfrac{3}{4}\right)\cdot\dfrac{1}{3}-\dfrac{2}{7}\cdot\left(3,5\right)^2\)
\(=\left(\dfrac{7}{8}-\dfrac{6}{8}\right)\cdot\dfrac{1}{3}-\dfrac{2}{7}\cdot\dfrac{49}{4}\)
\(=\dfrac{1}{8}\cdot\dfrac{1}{3}-\dfrac{7}{2}\)
\(=\dfrac{1}{24}-\dfrac{7}{2}\)
\(=\dfrac{1}{24}-\dfrac{84}{24}\)
\(=-\dfrac{83}{24}\)
#データネ

`(7/8-3/4)xx1/3-2/7xx(3,5)^2`

`=(7/8-6/8)xx1/3-2/7xx12,25`

`=1/8xx1/3-2/7xx12,25`

`=1/24-7/2`

`=1/24-84/24`

`=-83/24`

Bài 2: 

a: \(=\dfrac{7}{9}\left(\dfrac{7}{6}-\dfrac{19}{20}-\dfrac{1}{15}\right)+\dfrac{22}{5}\cdot\dfrac{1}{24}\)

\(=\dfrac{7}{9}\cdot\dfrac{3}{20}+\dfrac{22}{120}=\dfrac{7}{60}+\dfrac{11}{60}=\dfrac{18}{60}=\dfrac{3}{10}\)

b: \(=\left(\dfrac{35-32}{60}\right)^2+\dfrac{4}{5}\cdot\dfrac{70-45}{80}\)

\(=\dfrac{1}{400}+\dfrac{4\cdot25}{400}=\dfrac{101}{400}\)

3: \(\left|x-\dfrac{3}{4}\right|-\dfrac{1}{2}=0\)

\(\Leftrightarrow\left|x-\dfrac{3}{4}\right|=\dfrac{1}{2}\)

\(\Leftrightarrow\left[{}\begin{matrix}x-\dfrac{3}{4}=\dfrac{1}{2}\\x-\dfrac{3}{4}=-\dfrac{1}{2}\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{5}{4}\\x=\dfrac{1}{4}\end{matrix}\right.\)

`a)4/5+5 1/2 xx (4,5-2)+7/10`

`=4/5+11/2*2,5+7/10`

`=0,8+2,2+0,7`

`=3+0,7=3,7`

`b)125%xx 17/4:(1 5/16-0,5)+2008`

`=1,25xx4,25:13/16+2008`

`=85/13+2008`

`=2014 7/13`

`c)5/11+(16/11+1)`

`=5/11+1+5/11+1`

`=2+10/11=32/11`

`d)3/17+11/4+5/8+14/17+3/8`

`=3/17+14/17+5/8+3/8+11/4`

`=1+1+11/4`

`=19/4`

a) 

\(\dfrac{4}{5}+5\dfrac{1}{2}x\left(4,5-2\right)=\dfrac{7}{10}\)

<=> \(\dfrac{11}{2}x\times2,5=\dfrac{7}{10}-\dfrac{4}{5}=\dfrac{-1}{10}\)

<=> \(\dfrac{55}{4}x=\dfrac{-1}{10}< =>x=\dfrac{-2}{275}\)

b) \(125\%\times\dfrac{17}{4}:\left(1\dfrac{5}{16}-0,5\right)+2008\)

= \(\dfrac{85}{16}:\left(\dfrac{21}{16}-\dfrac{1}{2}\right)+2008=\dfrac{85}{16}:\dfrac{13}{16}+2008=\dfrac{26189}{13}\)

c) \(\dfrac{5}{11}+\left(\dfrac{16}{11}+1\right)\)

= \(\dfrac{21}{11}+1=\dfrac{32}{11}\)

d) \(\left(\dfrac{3}{17}+\dfrac{14}{17}\right)+\left(\dfrac{5}{8}+\dfrac{3}{8}\right)+\dfrac{11}{4}\)

= 1 + 1 + \(\dfrac{11}{4}\) = \(\dfrac{19}{4}\)

a/ \(x-y-z=0\) \(\Leftrightarrow\left\{{}\begin{matrix}x-z=y\\y-x=-z\\y+z=x\end{matrix}\right.\)

\(\Leftrightarrow\left(1-\dfrac{z}{x}\right)\left(1-\dfrac{x}{y}\right)\left(1+\dfrac{y}{z}\right)\)

\(=\left(\dfrac{x}{x}-\dfrac{z}{x}\right)\left(\dfrac{y}{y}-\dfrac{x}{y}\right)\left(\dfrac{z}{z}+\dfrac{y}{z}\right)\)

\(=\dfrac{x-z}{x}.\dfrac{y-x}{y}.\dfrac{z+y}{z}\)

\(=\dfrac{y}{x}.\dfrac{-z}{y}.\dfrac{x}{z}=-1\)

b/ \(M=\dfrac{3a-b}{2a+7}+\dfrac{3b-a}{2b-7}\)

\(=\dfrac{3a-b}{2a+\left(a-b\right)}+\dfrac{3b-a}{2b-\left(a-b\right)}\) (do \(a-b=7\))

\(=\dfrac{3a-b}{2a+a-b}+\dfrac{3b-a}{2b-a+b}\)

\(=\dfrac{3a-b}{3a-b}+\dfrac{3b-a}{3b-a}\)

\(=1+1=2\)