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0,(12) : (x - 1) = 1,(6) : 0,(4)
=> 0,(1) .12 : (x - 1) = [0,(1) . 6 + 1] : [0,(1) . 4]
=> 1/9 . 12 :(x - 1) = (1/9 . 6 + 1) : (1/9 . 4)
=> 4/3 :(x - 1) = 5/3 : 4/9
=> 4/3 : (x - 1) = 15/4
=> x - 1 = 4/3 : 15/4
=> x - 1 = 16/45
=> x = 16/45 + 1
=> x = 61/45
\(\dfrac{12}{99}\):(x-1)=\(\dfrac{5}{3}\):\(\dfrac{4}{9}\)
x-1=\(\dfrac{16}{495}\)
x=\(\dfrac{511}{495}\)
\(0,\left(12\right):\left(x-1\right)=1,\left(6\right):0,\left(4\right)\)
\(\Rightarrow\dfrac{12}{99}:\left(x-1\right)=\dfrac{5}{3}:\dfrac{4}{9}\)
\(\Rightarrow\dfrac{4}{33}:\left(x-1\right)=\dfrac{5}{3}.\dfrac{9}{4}\)
\(\Rightarrow\dfrac{4}{33}:\left(x-1\right)=\dfrac{15}{4}\)
\(\Rightarrow x-1=\dfrac{4}{33}:\dfrac{15}{4}\)
\(\Rightarrow x-1=\dfrac{16}{495}\)
\(\Rightarrow x=\dfrac{16}{495}+1\Rightarrow x=\dfrac{511}{495}\)
Còn cách biến đổi làm sao thì bạn xem ở đây nhá https://diendan.hocmai.vn/threads/doi-so-thap-phan-1-4-51-ra-phan-so-toi-gian.393734/
Cho ví dụ luôn biến đổi \(1,\left(6\right)\) sang phân số là: \(1,\left(6\right)=1+0,\left(6\right)=1+\dfrac{2}{3}=\dfrac{3}{3}+\dfrac{2}{3}=\dfrac{5}{3}\)
Chúc bạn học tốt 
a, Ta thấy : \(\left\{{}\begin{matrix}\left(2a+1\right)^2\ge0\\\left(b+3\right)^2\ge0\\\left(5c-6\right)^2\ge0\end{matrix}\right.\)\(\forall a,b,c\in R\)
\(\Rightarrow\left(2a+1\right)^2+\left(b+3\right)^2+\left(5c-6\right)^2\ge0\forall a,b,c\in R\)
Mà \(\left(2a+1\right)^2+\left(b+3\right)^2+\left(5c-6\right)^2\le0\)
Nên trường hợp chỉ xảy ra là : \(\left(2a+1\right)^2+\left(b+3\right)^2+\left(5c-6\right)^2=0\)
- Dấu " = " xảy ra \(\left\{{}\begin{matrix}2a+1=0\\b+3=0\\5c-6=0\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}a=-\dfrac{1}{2}\\b=-3\\c=\dfrac{6}{5}\end{matrix}\right.\)
Vậy ...
b,c,d tương tự câu a nha chỉ cần thay số vào là ra ;-;
a, \(\Leftrightarrow x^2+2x+1+\left|x+10\right|-x^2-12=0\)
\(\Leftrightarrow\left|x+10\right|+2x-11=0\)
ta có ; | x+10| = x+10 khi x+10\(\ge\)0 hay x \(\ge\)-10
|x+10| = -x-10 khi x+10<0 hay x<-10
vs x\(\ge\)-10 ta có: x+10+2x-11=0 \(\Leftrightarrow\)3x=1 \(\Leftrightarrow\)x= \(\frac{1}{3}\)( thỏa mãn )
vs x< -10 ta có (tự thay vào r tính típ)
vậy x=...............
b, lm tg tự
3: \(\left|x-\dfrac{3}{4}\right|-\dfrac{1}{2}=0\)
\(\Leftrightarrow\left|x-\dfrac{3}{4}\right|=\dfrac{1}{2}\)
\(\Leftrightarrow\left[{}\begin{matrix}x-\dfrac{3}{4}=\dfrac{1}{2}\\x-\dfrac{3}{4}=-\dfrac{1}{2}\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{5}{4}\\x=\dfrac{1}{4}\end{matrix}\right.\)
B1 :
\(\frac{0,1\left(6\right)+0,\left(3\right)}{0,\left(3\right)+1,1\left(6\right)}\) . x = 0,(2)
=\(\frac{0,5}{1,5}\).x=0,(2)
x=0,(2):\(\frac{0,5}{1,5}\)
x=0,(6)=\(\frac{2}{3}\)
b2:
[12,(1) - 2,3(6)] : 4,(21)
=9,7(4):4,(21)
=\(\frac{9,7\left(4\right)}{4,\left(21\right)}\)
a) \(\left[0,\left(37\right)+0,\left(62\right)\right]\cdot x=10\)
=> \(\left[\frac{37}{99}+\frac{62}{99}\right]\cdot x=10\)
=> \(1\cdot x=10\Rightarrow x=10\)
b) \(\frac{0,\left(12\right)}{1,\left(6\right)}=\frac{\frac{12}{99}}{\frac{5}{3}}=\frac{12}{99}\cdot\frac{3}{5}=\frac{4}{55}\)
=> \(\frac{4}{55}=x:0,\left(4\right)\)
=> \(\frac{4}{55}=x:\frac{4}{9}\)
=> \(x:\frac{4}{9}=\frac{4}{55}\)
=> \(x=\frac{4}{55}\cdot\frac{4}{9}=\frac{16}{495}\)