Ta có:
\(\begin{cases}x-\frac{3}{5}>0\rightarrow x>\frac{3}{5}\\x+\frac{2}{7}< 0\rightarrow x< \frac{-2}{7}\end{cases}\) (Vô lý)
\(\begin{cases}x-\frac{3}{5}< 0\rightarrow x< \frac{3}{5}\\x+\frac{2}{7}>0\rightarrow x>\frac{-2}{7}\end{cases}\) (Hợp lý)
tìm x
n) \(\frac{x+1}{2008}=\frac{502}{x+1}\)
p) \(\left|\frac{5}{4}x-\frac{7}{2}\right|-\left|\frac{5}{8}x+\frac{3}{5}\right|=0\)
\(\left|x+\frac{1}{2}\right|+\left|x+\frac{1}{6}\right|+\left|x+\frac{1}{12}\right|+\left|x=\frac{1}{20}\right|+...+\left|x+\frac{1}{101}\right|=101x\)
2. Tìm x, y, z biết\(\left(2x+1\right)^{2008}+\left(y-\frac{2}{5}\right)^{2008}+\left|x+y+z\right|=0\)
3.Tìm x\(a,2009-\left|x-2009\right|=x\)
\(b,\left|3x+2\right|=\left|5x-3\right|\)
1.Tính:
\(a,A=\sqrt{12\frac{1}{4}}.\left(\frac{-2}{7}\right)^2-\left[2,\left(4\right).2\frac{5}{11}\right]:\left(\frac{-42}{5}\right)\)
\(B=\frac{1}{3}+\frac{2}{3^2}+\frac{3}{3^3}+\frac{4}{3^4}+...+\frac{2016}{3^{2016}}\)
2. Tìm x,y,z biết:
a) \(\left|x+1\right|+\left|x+2\right|+\left|x+4\right|+\left|x+5\right|-6x=0\)
b) \(\sqrt{\left(x+\sqrt{5}\right)^2}+\sqrt{\left(y+\sqrt{3}\right)^2}+\left|x-y-z\right|=0\)
c) \(\frac{x-2}{2}=\frac{y-3}{3}=\frac{z-3}{4}\) và x-2y+3z=14.
d) \(5^x+5^{x+1}+5^{x+2}=3875\).
3. a) Cho bốn số a,b,c,d>0 thỏa mãn: \(\frac{1}{c}=\frac{ }{1}2.\left(\frac{1}{b}+\frac{1}{a}\right)\)và b là trung bình cộng của a và c. Chứng minh rằng bốn số đó lập nên một tỉ lệ thức.
b) Cho tỉ lệ thức: \(\frac{2a+13b}{3a-7b}=\frac{2c+13d}{3c-7d}\) (với a,b,c,d khác 0)
Chứng minh rằng: \(\frac{a}{b}=\frac{c}{d}\)
Bài 4.1: Tìm x, biết
a) \(4\left|3x-1\right|+\left|x\right|-2\left|x-5\right|+7\left|x-3\right|=12\)
b) \(3\left|x+4\right|-\left|2x+1\right|-5\left|x+3\right|+\left|x-9\right|=5\)
c) \(\left|2\frac{1}{5}-x\right|+\left|x-\frac{1}{5}\right|+8\frac{1}{5}=1,2\)
d) \(2\left|x+3\frac{1}{2}\right|+\left|x\right|-3\frac{1}{2}=\left|2\frac{1}{5}-x\right|\)
Tìm x biết :
1) \(\left(\frac{2}{5}-x\right):1\frac{1}{3}+\frac{1}{2}=-4\)
2) \(\left(-3+\frac{3}{x}-\frac{1}{3}\right):\left(1+\frac{2}{5}+\frac{2}{3}\right)=-\frac{5}{4}\)
3) \(\frac{-3x}{4}.\left(\frac{1}{x}+\frac{2}{7}\right)=0\)
4) \(3-\frac{1-\frac{1}{2}}{1+\frac{1}{x}}=2\frac{2}{3}\)
5) \(3.\left|4x-1\right|-2=19\)
6) \(\left(2x+\frac{1}{3}\right)^2=\frac{9}{16}\)
7) \(\left|x+2\right|-6x=1\)
8) \(\left|x-3\right|+\left|x-2\right|=7\)
9) \(\left|2x+1\right|+\left|x+8\right|=4x\)
10) \(4^x+4^{x+3}=4160\)
giúp mình nhé 
tìm x
a) 2.\(\left|x.\frac{2}{3}\right|-1=0\)
b) \(3-\frac{5}{2}.\left|\frac{2}{5}-x\right|=0\)
Tìm x biết :
a) \(\left[\left(6\frac{3}{5}-3\frac{3}{14}\right).2,5\right]:\left(21-1,25\right)=x:5\frac{5}{6}\)
b) \(\left(4-\frac{3}{4}\right):\left(2\frac{1}{3}-1\frac{1}{9}\right)=31x:\left(45\frac{10}{63}-44\frac{25}{84}\right)\)
c) \(\frac{x-1}{x+5}=\frac{6}{7}\)
d) \(\frac{x^2}{6}=\frac{24}{25}\)
e) \(\frac{x-2}{x-1}=\frac{x+4}{x+7}\)
giúp mình nhé
Tìm x, biết
\(\frac{0.\left(3\right)+0.\left(384615\right)+\frac{3}{13}.x}{0.0\left(3\right)+13}=\frac{50}{85}\)
Đề Bài : Tìm x; y; z \(\in\) Q , biết :
a) \(\left|x+\frac{3}{4}\right|\) + \(\left|y-\frac{1}{5}\right|\)+\(\left|x+y+z\right|\) = 0
b) \(\left|x+\frac{3}{4}\right|+\left|y-\frac{2}{3}\right|+\left|z+\frac{1}{2}\right|=0\)
c) |x| +x = 0
d) \(\left|x+1\right|+\left|x^2-1\right|=0\)
