KL
1
K
Khách
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KL
1 tháng 8 2017
\(\dfrac{-8}{13}+\dfrac{-7}{17}+\dfrac{21}{13}\le x\le\dfrac{-9}{14}+3+\dfrac{5}{-14}\)
=> \(\dfrac{10}{17}\le x\le2\)
=> \(\dfrac{10}{17}\le\dfrac{17x}{17}\le\dfrac{34}{17}\)
=> 10 \(\le17x\le34\)
=> x = 1; 2 (thỏa mãn)
@Khánh Linh
15 tháng 8 2017
\(\dfrac{1-x}{2017}+\dfrac{2-x}{2016}=\dfrac{3-x}{2015}+\dfrac{4-x}{2014}\)
\(\Leftrightarrow\left(\dfrac{1-x}{2017}+1\right)+\left(\dfrac{2-x}{2016}+1\right)=\left(\dfrac{3-x}{2015}+1\right)+\left(\dfrac{4-x}{2014}+1\right)\)
\(\Leftrightarrow\dfrac{2018-x}{2017}+\dfrac{2018-x}{2016}=\dfrac{2018-x}{2015}+\dfrac{2018-x}{2014}\)
\(\Leftrightarrow\dfrac{2018-x}{2017}+\dfrac{2018-x}{2016}-\dfrac{2018-x}{2015}-\dfrac{2018-x}{2014}=0\)
\(\Leftrightarrow\left(2018-x\right)\left(\dfrac{1}{2017}+\dfrac{1}{2016}-\dfrac{1}{2015}-\dfrac{1}{2014}\right)=0\)
Mà \(\dfrac{1}{2017}+\dfrac{1}{2016}-\dfrac{1}{2015}-\dfrac{1}{2014}\ne0\)
\(\Leftrightarrow2018-x=0\Leftrightarrow x=2018\)
Vậy ....
KL
1
26 tháng 7 2017
\(\dfrac{x-1}{2}=\dfrac{8}{x-1}\)
\(\Rightarrow\left(x-1\right)\left(x-1\right)=16\)
\(\Rightarrow\left(x-1\right)^2=16\)
\(\Rightarrow\left(x-1\right)^2=\pm4\)
\(\Rightarrow\left[{}\begin{matrix}x-1=4\Rightarrow x=5\\x-1=-4\Rightarrow x=-3\end{matrix}\right.\)
26 tháng 7 2017
cho mk sửa lại
tacó:
\(\dfrac{-64}{125}=\left(\dfrac{-4}{5}\right)^3\)
suy ra\(\dfrac{2}{3}-\dfrac{3}{5}x=\dfrac{-4}{5}\)
\(\dfrac{3}{5}x=\dfrac{2}{3}-\dfrac{-4}{5}\)
\(\dfrac{3}{5}x=\dfrac{22}{15}\)
\(x=\dfrac{22}{15}:\dfrac{3}{5}\)
\(x=\dfrac{22}{9}\)
26 tháng 7 2017
ta có:
\(\dfrac{-64}{125}=\left(\dfrac{-16}{5}\right)^3\)
suy ra \(\dfrac{2}{3}-\dfrac{3}{5}x=\dfrac{-16}{5}\)
\(\dfrac{3}{5}x=\dfrac{2}{3}-\dfrac{-16}{5}\)
\(\dfrac{3}{5}x=\dfrac{58}{15}\)
\(x=\dfrac{58}{15}:\dfrac{3}{5}\)
\(x=\dfrac{58}{9}\)
16 tháng 3 2017
a, (0.5-\(\dfrac{2}{3}\))x=\(\dfrac{7}{12}\)
\(\Leftrightarrow\)\(\dfrac{-1}{6}\)x=\(\dfrac{7}{12}\)
\(\Leftrightarrow\)x= \(\dfrac{-7}{2}\)=-3,5
b.x \(\div\)4\(\dfrac{1}{3}\)=-2,5
\(\Leftrightarrow\) x \(\div\)\(\dfrac{13}{3}\)=-2,5
\(\Leftrightarrow\) x = -2,5 \(\times\)\(\dfrac{13}{3}\)
\(\Leftrightarrow\) x = \(\dfrac{-65}{6}\)
16 tháng 3 2017
x.(0.5-\(\dfrac{2}{3}\))=\(\dfrac{7}{12}\)
x=\(\dfrac{-7}{2}\)
MV
24 tháng 7 2017
\(x:\dfrac{1}{2}+x:\dfrac{1}{4}+x:\dfrac{1}{8}+...+x:\dfrac{1}{512}=511\\ 2x+4x+8x+..+512x=511\\ x\left(2+4+8+...+512\right)=511\\ x\left(2^1+2^2+2^3+...+2^9\right)=511\\ \)
Gọi \(S=2^1+2^2+2^3+...+2^9\)
\(2S=2^2+2^3+2^4+...+2^{10}\\ 2S-S=\left(2^2+2^3+2^4+...+2^{10}\right)-\left(2^1+2^2+2^3+...+2^9\right)\\ S=2^{10}-2\)
\(x\left(2^{10}-2\right)=511\\ 2x\left(2^9-1\right)=511\\ 2x\left(512-1\right)=511\\ 2x\cdot511=511\\ 2x=1\\ x=\dfrac{1}{2}\)
Vậy \(x=\dfrac{1}{2}\)
26 tháng 7 2017
1) \(-3+\dfrac{1}{2}< x< \dfrac{7}{2}+\dfrac{1}{3}\)
\(\Rightarrow-\dfrac{5}{2}< x< \dfrac{23}{6}\)
\(\Rightarrow-2,5< x< 3,8\left(3\right)\)
Mà x là số nguyên nên:
\(x\in\left\{-2;-1;0;1;2;3\right\}\)
DT
Đỗ Thanh Hải
CTVVIP
8 tháng 8 2017
\(x+\left|\dfrac{1}{2}-\dfrac{1}{3}\right|=\left|\dfrac{-2}{3}-\dfrac{1}{4}\right|\)
\(x+\left|\dfrac{1}{6}\right|=\left|\dfrac{-11}{12}\right|\)
\(x+\dfrac{1}{6}=\dfrac{11}{12}\)
\(x=\dfrac{11}{12}-\dfrac{1}{6}\)
\(x=\dfrac{3}{4}\)
Vậy ...
\(\dfrac{0,3.x+2,5}{x}-3=17\)
<=> \(\dfrac{0,3.x+2,5}{x}=20\)
<=> 0,3.x + 2,5 = 20x
<=> 2,5 = 20x - 0,3.x
<=> 2,5 = 19,7.x
<=> x = \(\dfrac{25}{197}\)
@Khánh Linh