Bài 1:

a) \(0,\left(3\right)+3\frac{1}{3}+0,\left(31\right)\)

\(=\frac{1}{3}+\frac{10}{3}+\frac{31}{99}\)

\(=\frac{11}{3}+\frac{31}{99}\)

\(=\frac{394}{99}.\)

b) \(\frac{4}{9}+1,2\left(31\right)-0,\left(13\right)\)

\(=\frac{4}{9}+\frac{1219}{990}-\frac{13}{99}\)

\(=\frac{553}{330}-\frac{13}{99}\)

\(=\frac{139}{90}.\)

Bài 2:

\(0,\left(37\right).x=1\)

\(\Rightarrow\frac{37}{99}.x=1\)

\(\Rightarrow x=1:\frac{37}{99}\)

\(\Rightarrow x=\frac{99}{37}\)

Vậy \(x=\frac{99}{37}.\)

Chúc bạn học tốt!

Giải:

a) \(\dfrac{4}{9}+1,2\left(31\right)-0,\left(13\right)\)

\(=\dfrac{4}{9}+\dfrac{1219}{990}-\dfrac{13}{99}\)

\(=\dfrac{553}{330}-\dfrac{13}{99}\)

\(=\dfrac{139}{90}\)

Vậy giá trị của biểu thức trên là \(\dfrac{139}{90}\).

b) \(2\dfrac{1}{2}-3,4\left(12\right)-\dfrac{4}{3}\)

\(=\dfrac{5}{2}-\dfrac{563}{165}-\dfrac{4}{3}\)

\(=-\dfrac{301}{330}-\dfrac{4}{3}\)

\(=-\dfrac{247}{110}\)

Vậy giá trị của biểu thức trên là \(-\dfrac{247}{110}\).

Chúc bạn học tốt!

a: \(=\dfrac{5}{2}-\dfrac{563}{165}-\dfrac{4}{3}+\dfrac{1}{3}\left(1-3-\dfrac{1}{2}\right)\)

\(=\dfrac{-247}{110}+\dfrac{1}{3}\cdot\dfrac{-5}{2}=\dfrac{-508}{165}\)

b: \(=\dfrac{4}{9}+\dfrac{1219}{990}-\dfrac{13}{99}=\dfrac{139}{90}\)

b) \(\dfrac{3}{4}+\dfrac{1}{4}:x=\dfrac{2}{5}\)

\(\Rightarrow\dfrac{1}{4}:x=\dfrac{2}{5}-\dfrac{2}{4}\)

\(\Rightarrow\dfrac{1}{4}:x=-\dfrac{1}{10}\)

\(\Rightarrow x=\dfrac{1}{4}:\left(-\dfrac{1}{10}\right)\)

\(\Rightarrow x=-\dfrac{3}{2}\)

a: \(\Leftrightarrow\dfrac{x+1}{2x+1}=\dfrac{x+4}{2x+6}\)

=>(x+1)(2x+6)=(2x+1)(x+4)

\(\Leftrightarrow2x^2+6x+2x+6=2x^2+8x+x+4\)

=>9x+4=8x+6

=>x=2

b: \(x^2+5x=0\)

=>x(x+5)=0

=>x=0 hoặc x=-5

a: 2x(x-1/7)=0

=>x(x-1/7)=0

=>x=0 hoặc x=1/7

b: \(\dfrac{3}{4}+\dfrac{1}{4}:x=\dfrac{2}{5}\)

\(\Leftrightarrow\dfrac{1}{4}:x=\dfrac{2}{5}-\dfrac{3}{4}=\dfrac{8}{20}-\dfrac{15}{20}=\dfrac{-7}{20}\)

nên \(x=\dfrac{-1}{4}:\dfrac{7}{20}=\dfrac{-20}{4\cdot7}=\dfrac{-5}{7}\)

c: \(\Leftrightarrow\dfrac{41}{9}:\dfrac{41}{18}-7< x< \left(3.2:3.2+\dfrac{45}{10}\cdot\dfrac{31}{45}\right):\left(-21.5\right)\)

\(\Leftrightarrow2-7< x< \dfrac{\left(1+3.1\right)}{-21.5}\)

\(\Leftrightarrow-5< x< \dfrac{-41}{215}\)

mà x là số nguyên

nên \(x\in\left\{-4;-3;-2;-1\right\}\)

1, a/ \(\left|x\right|=\dfrac{1}{2}\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{1}{2}\\x=\dfrac{-1}{2}\end{matrix}\right.\)

Vậy .............

b/ \(\left|x\right|=3,12\Leftrightarrow\left[{}\begin{matrix}x=3,12\\x=-3,12\end{matrix}\right.\)

Vậy ...........

c/ \(\left|x\right|=0\Leftrightarrow x=0\)

Vậy ..........

d/ \(\left|x\right|=2\dfrac{1}{7}\) \(\Leftrightarrow\left[{}\begin{matrix}x=2\dfrac{1}{7}\\x=-2\dfrac{1}{7}\end{matrix}\right.\)

Vậy ..............

2, a/ \(\left|x\right|=2,1\Leftrightarrow\left[{}\begin{matrix}x=2,1\\x=-2,1\end{matrix}\right.\)

Vậy ...........

b/ \(\left|x\right|=\dfrac{17}{9}\) ; \(x< 0\)

\(\Leftrightarrow x=-\dfrac{17}{9}\)

Vậy ..........

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

Vậy ...........

d/ \(\left|x\right|=0,35\) ; \(x>0\Leftrightarrow x=0,35\)

3, a/ \(\left|x-1,7\right|=2,3\)

\(\Leftrightarrow\left[{}\begin{matrix}x-1,7=2,3\\x-1,7=-2,3\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=4\\x=-0,6\end{matrix}\right.\)

Vậy ...........

b/ \(\left|x+\dfrac{3}{4}\right|-\dfrac{1}{3}=0\)

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

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

\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{-5}{12}\\x=-\dfrac{13}{12}\end{matrix}\right.\)

Vậy ...........

Đề dễ lắm sao ko tự làm đi