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17 tháng 4 2017
a, \(\left(2,8x-32\right):\dfrac{2}{3}=-90\)
\(\Rightarrow2,8x-32=-60\)
\(\Rightarrow2,8x=-28\)
\(\Rightarrow x=-10\)
Vậy x = -10
b, \(\left(4,5-2x\right):1\dfrac{4}{7}=\dfrac{11}{14}\)
\(\Rightarrow\left(4,5-2x\right):\dfrac{11}{7}=\dfrac{11}{14}\)
\(\Rightarrow4,5-2x=\dfrac{121}{98}\)
\(\Rightarrow2x=\dfrac{160}{49}\)
\(\Rightarrow x=\dfrac{80}{49}\)
Vậy \(x=\dfrac{80}{49}\)
C
17 tháng 4 2017
\(a,\left(2,8x-32\right):\dfrac{2}{3}=-90\)
\(2,8x-32=-90.\dfrac{2}{3}\)
\(2,8x-32=-60\)
\(2,8x=-60+32\)
\(2,8x=-28\)
\(x=-28:2,8\)
\(x=-10\)
Vậy \(x=-10\)
\(b,\left(4,5-2x\right):1\dfrac{4}{7}=\dfrac{11}{14}\)
\(\left(4,5-2x\right):\dfrac{11}{7}=\dfrac{11}{14}\)
\(4,5-2x=\dfrac{11}{14}.\dfrac{11}{7}\)
\(4,5-2x=\dfrac{121}{98}\)
\(2x=4,5-\dfrac{121}{98}\)
\(2x=\dfrac{160}{49}\)
\(x=\dfrac{160}{49}:2\)
\(x=\dfrac{80}{49}\)
Vậy \(x=\dfrac{80}{49}\)
Q
21 tháng 6 2017
a) \(\dfrac{x+1}{32}=\dfrac{2}{x+1}\)
\(\Leftrightarrow\dfrac{x+1}{32}=\dfrac{2}{x+1}\left(đk:x\ne1\right)\)
\(\Leftrightarrow\left(x+1\right)\left(x+1\right)=64\)
\(\Leftrightarrow\left(x+1\right)^2-64=0\)
\(\Leftrightarrow x^2+2x+1-64=0\)
\(\Leftrightarrow x^2+6x-63=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{-2+16}{2}\\x=\dfrac{-2-16}{2}\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=7\\x=-9\end{matrix}\right.\left(đk:x\ne-1\right)\)
\(\Leftrightarrow\left[{}\begin{matrix}x=7\\x=-9\end{matrix}\right.\)
Vậy \(x_1=-9;x_2=7\)
b) \(\dfrac{x+1}{5}=\dfrac{7}{x-1}\)
\(\Leftrightarrow\dfrac{x+1}{5}=\dfrac{7}{x-1}\left(đk:x\ne1\right)\)
\(\Leftrightarrow\left(x+1\right)\left(x-1\right)=35\)
\(\Leftrightarrow\left(x+1\right)\left(x-1\right)-35=0\)
\(\Leftrightarrow x^2-1-35=0\)
\(\Leftrightarrow x^2-36=0\)
\(\Leftrightarrow x^2=36\)
\(\Leftrightarrow\left[{}\begin{matrix}x=6\\x=-6\end{matrix}\right.\left(đk:x\ne1\right)\)
\(\Leftrightarrow\left[{}\begin{matrix}x=6\\x=-6\end{matrix}\right.\)
Vậy \(x_1=-6;x_2=6\)
c) \(\left|4,5-2x\right|:1\dfrac{7}{4}=\dfrac{11}{14}\)
\(\Leftrightarrow\left|4,5-2x\right|:\dfrac{11}{4}=\dfrac{11}{4}\)
\(\Leftrightarrow\left|4,5-2x\right|\cdot\dfrac{4}{11}=\dfrac{11}{14}\)
\(\Leftrightarrow\dfrac{4}{11}\cdot\left|4,5-2x\right|=\dfrac{11}{14}\)
\(\Leftrightarrow\left|4,5-2x\right|=\dfrac{121}{56}\)
\(\Leftrightarrow\left[{}\begin{matrix}4,5-2x=\dfrac{121}{56}\\4,5-2x=-\dfrac{121}{56}\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{131}{112}\\x=\dfrac{373}{112}\end{matrix}\right.\)
Vậy \(x_1=\dfrac{131}{112};x_2=\dfrac{373}{112}\)
21 tháng 6 2017
a) \(\dfrac{x+1}{32}=\dfrac{2}{x+1}\)
\(\Rightarrow\left(x+1\right)\left(x+1\right)=32.2\)
\(\Rightarrow\left(x+1\right)^2=64\)
\(\Rightarrow\left(x+1\right)^2=8^2\)
\(\Rightarrow x+1=8\)
\(\Rightarrow x=8-1\)
\(\Rightarrow x=7\left(TM\right)\)
Vậy \(x=7\) là giá trị cần tìm
b) \(\dfrac{x+1}{5}=\dfrac{7}{x-1}\)
\(\Rightarrow\left(x+1\right)\left(x-1\right)=7.5\)
\(\Rightarrow\left[{}\begin{matrix}x+1=7\\x-1=5\end{matrix}\right.\) \(\Rightarrow x=6\left(TM\right)\)
Vậy \(x=6\) là giá trị cần tìm
c) \(\left|4,5-2x\right|:1\dfrac{7}{4}=\dfrac{11}{14}\)
\(\left|\dfrac{45}{10}-2x\right|:\dfrac{11}{4}=\dfrac{11}{4}\)
\(\left|\dfrac{9}{2}-2x\right|=\dfrac{11}{14}.\dfrac{11}{4}\)
\(\left|\dfrac{9}{2}-2x\right|=\dfrac{121}{56}\)
\(\Rightarrow\left[{}\begin{matrix}\dfrac{9}{2}-2x=\dfrac{121}{56}\\\dfrac{9}{2}-2x=\dfrac{-121}{56}\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}2x=\dfrac{131}{56}\\2x=\dfrac{373}{56}\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x=\dfrac{131}{112}\\x=\dfrac{373}{112}\end{matrix}\right.\)
Vậy \(x\in\left\{\dfrac{131}{112};\dfrac{373}{112}\right\}\) là giá trị cần tìm
26 tháng 5 2017
Anh làm lại câu b)
\(\left(4,5-200\%x\right).1\dfrac{4}{7}=\dfrac{11}{14}\\ < =>\left(\dfrac{9}{2}-2x\right).\dfrac{11}{7}=\dfrac{11}{14}\\ =>\dfrac{9}{2}-2x=\dfrac{\dfrac{11}{14}}{\dfrac{11}{7}}=\dfrac{1}{2}\\ =>2x=\dfrac{9}{2}-\dfrac{1}{2}=4\\ =>x=\dfrac{4}{2}=2\)
26 tháng 5 2017
a, \(3x+\dfrac{1}{8}=2\dfrac{3}{4}\\ < =>3x+\dfrac{1}{8}=\dfrac{11}{4}\\ =>3x=\dfrac{11}{4}-\dfrac{1}{8}=\dfrac{21}{8}\\ =>x=\dfrac{\dfrac{21}{8}}{3}=\dfrac{7}{8}\)
b, \(\left(4,5-200\%x\right).1\dfrac{4}{7}=\dfrac{11}{14}\\ < =>\left(4,5-2x\right).\dfrac{11}{7}=\dfrac{11}{4}\\ =>4,5-2x=\dfrac{11}{4}:\dfrac{11}{7}=\dfrac{7}{4}\\ =>2x=4,5-\dfrac{7}{4}=\dfrac{11}{4}\\ =>x=\dfrac{\dfrac{11}{4}}{2}=\dfrac{11}{8}\)
Q
25 tháng 6 2017
1) \(x+\dfrac{30}{100}x=-1,31\)
\(\Leftrightarrow x+\dfrac{3}{10}x=-\dfrac{131}{100}\)
\(\Leftrightarrow100x+30x=-131\)
\(\Leftrightarrow130x=-131\)
\(\Leftrightarrow x=-\dfrac{131}{130}\)
Vậy \(x=-\dfrac{131}{130}\)
b) \(\left(4,5-2x\right)\cdot\left(-1\dfrac{4}{7}\right)=\dfrac{11}{4}\)
\(\Leftrightarrow\left(\dfrac{9}{2}-2x\right)\cdot\left(-\dfrac{4}{7}\right)=\dfrac{11}{4}\)
\(\Leftrightarrow-\dfrac{18}{7}+\dfrac{8}{7}x=\dfrac{11}{4}\)
\(\Leftrightarrow-72+32x=77\)
\(\Leftrightarrow32x=77+72\)
\(\Leftrightarrow32x=149\)
\(\Leftrightarrow x=\dfrac{149}{32}\)
Vậy \(x=\dfrac{149}{32}\)
2 tháng 4 2017
Tìm x biết:
\(\left(4,5-2x\right).1\dfrac{4}{7}=\dfrac{11}{4}\)
\(\Leftrightarrow\left(4,5-2x\right)=\dfrac{11}{4}:1\dfrac{4}{7}\)
\(\Leftrightarrow4,5-2x=\dfrac{7}{4}\)
\(\Leftrightarrow2x=4,5-\dfrac{7}{4}\)
\(\Leftrightarrow2x=\dfrac{11}{4}\)
Vậy \(x=\dfrac{11}{8}\)
Tìm số nguyên x biết:
Theo đề bài, ta có:
\(4\dfrac{1}{3}\left(\dfrac{1}{6}-\dfrac{1}{2}\right)\le x\le\dfrac{2}{3}\left(\dfrac{1}{3}-\dfrac{1}{2}-\dfrac{3}{4}\right)\)
\(\Leftrightarrow-\dfrac{13}{9}\le x\le-\dfrac{11}{18}\) hay \(-\dfrac{26}{18}\le x\le-\dfrac{11}{18}\)
\(\Leftrightarrow-1,\left(4\right)\le x\le-0,6\left(1\right)\)
Mà \(x\in Z\) nên x=-1
Vậy x = -1
30 tháng 8 2018
a) \(\left(3\dfrac{1}{3}-x\right)1\dfrac{1}{6}=\dfrac{7}{24}\)
\(\Leftrightarrow\left(\dfrac{10}{3}-x\right)\dfrac{7}{6}=\dfrac{7}{24}\)
\(\Leftrightarrow\dfrac{10}{3}-x=\dfrac{7}{24}:\dfrac{7}{6}\)
\(\Leftrightarrow\dfrac{10}{3}-x=\dfrac{1}{4}\)
\(\Leftrightarrow x=\dfrac{10}{3}-\dfrac{1}{4}\)
\(\Leftrightarrow x=\dfrac{37}{12}\).
b) \(\left(4,5-2x\right):\dfrac{3}{4}=1\dfrac{1}{3}\)
\(\Leftrightarrow\left(4,5-2x\right):\dfrac{3}{4}=\dfrac{4}{3}\)
\(\Leftrightarrow4,5-2x=\dfrac{4}{3}.\dfrac{3}{4}\)
\(\Leftrightarrow4,5-2x=1\)
\(\Leftrightarrow2x=4,5-1\)
\(\Leftrightarrow2x=3,5\)
\(\Leftrightarrow x=\dfrac{35}{2}\).
11 tháng 7 2017
\(a.-8:\left(4\dfrac{1}{5}x+\dfrac{3}{10}\right)=4\dfrac{4}{9}\)
\(4\dfrac{1}{5}x+\dfrac{3}{10}=\left(-8\right):4\dfrac{4}{9}\)
\(4\dfrac{1}{5}x+\dfrac{3}{10}=\dfrac{-9}{5}\)
\(4\dfrac{1}{5}x=\dfrac{-9}{5}-\dfrac{3}{10}\)
\(4\dfrac{1}{5}x=\dfrac{-21}{10}\)
\(x=\dfrac{-21}{10}:\dfrac{21}{5}\)
\(x=\dfrac{-1}{2}\)
Vay \(x=\dfrac{-1}{2}\).
\(b.4\dfrac{2}{3}-\left(\dfrac{3}{5}:x\right)=-20\%\)
\(\dfrac{14}{3}-\left(\dfrac{3}{5}:x\right)=\dfrac{-1}{5}\)
\(\dfrac{3}{5}:x=\dfrac{14}{3}-\dfrac{-1}{5}\)
\(\dfrac{3}{5}:x=\dfrac{73}{15}\)
\(x=\dfrac{3}{5}:\dfrac{73}{15}\)
\(x=\dfrac{9}{73}\)
Vay \(x=\dfrac{9}{73}\).
Câu c; d; e tương tự nhé.
11 tháng 4 2017
bài 1:
a) \(4\dfrac{1}{2}x:\dfrac{5}{12}=0,5\) ; b)\(1,5+1\dfrac{1}{4}x=\dfrac{2}{3}\)
\(\dfrac{9}{2}x:\dfrac{5}{12}=\dfrac{1}{2}\) \(\dfrac{3}{2}+\dfrac{5}{4}x=\dfrac{2}{3}\)
\(\dfrac{9}{2}x\) \(=\dfrac{1}{2}.\dfrac{5}{12}\) \(\dfrac{5}{4}x=\dfrac{2}{3}-\dfrac{3}{2}\)
\(\dfrac{9}{2}x\) \(=\dfrac{5}{24}\) \(\dfrac{5}{4}x=\dfrac{-5}{6}\)
\(x\) \(=\dfrac{5}{24}:\dfrac{9}{2}\) \(x=\dfrac{-5}{6}:\dfrac{5}{4}\)
\(x\) \(=\dfrac{5}{108}\) \(x=\dfrac{-2}{3}\)
c) Cho mình hỏi x ở đâu vậy ???
d)\(\left(x-5\right):\dfrac{1}{3}=\dfrac{2}{5}\) e)\(\left(4,5-2x\right):\dfrac{3}{4}=1\dfrac{1}{3}\)
\(\left(x-5\right)\) \(=\dfrac{2}{5}.\dfrac{1}{3}\) \(\left(\dfrac{9}{2}-2x\right):\dfrac{3}{4}=\dfrac{4}{3}\)
\(x-5\) \(=\dfrac{2}{15}\) \(\dfrac{9}{2}-2x\) =\(\dfrac{4}{3}.\dfrac{3}{4}\)
\(x\) \(=\dfrac{2}{15}+5\) \(\dfrac{9}{2}-2x=1\)
\(x\) \(=\dfrac{77}{15}\) \(2x=\dfrac{9}{2}-1\)
f) \(\left(2,7x-1\dfrac{1}{2}x\right):\dfrac{2}{7}=\dfrac{-21}{7}\) \(2x=\dfrac{7}{2}\)
\(\left(\dfrac{27}{10}x-\dfrac{3}{2}x\right):\dfrac{2}{7}=-3\) \(x=\dfrac{7}{2}:2\)
\(\left[x\left(\dfrac{27}{10}-\dfrac{3}{2}\right)\right]=-3.\dfrac{2}{7}\) \(x=\dfrac{7}{4}\)
\(x.\dfrac{6}{5}=\dfrac{-6}{7}\)
\(x=\dfrac{-6}{7}:\dfrac{6}{5}\)
\(x=\dfrac{-5}{7}\)
bài 2:
Theo bài ra ta có :\(\dfrac{a}{27}=\dfrac{-5}{9}=\dfrac{-45}{b}\)
\(\Rightarrow9a=27.\left(-5\right)\Rightarrow a=\dfrac{27.\left(-5\right)}{9}=-15\)
\(\Rightarrow\left(-5\right)b=\left(-45\right).9\Rightarrow b=\dfrac{\left(-45\right).9}{-5}=81\)
Vậy \(a=-15;b=81\)
14 tháng 4 2018
a)
\(\dfrac{1}{2}x+\dfrac{1}{8}x=\dfrac{3}{4}\\ x\left(\dfrac{1}{2}+\dfrac{1}{8}\right)=\dfrac{3}{4}\\ x\cdot\dfrac{5}{8}=\dfrac{3}{4}\\ x=\dfrac{3}{4}:\dfrac{5}{8}=\dfrac{6}{5}\)
b)
\(\left(2x-4,5\right):\dfrac{3}{4}-\dfrac{1}{3}=1\\\left(2x-\dfrac{9}{2}\right):\dfrac{3}{4}-\dfrac{1}{3}=1\\ \left(2x-\dfrac{9}{2}\right):\dfrac{3}{4}=1+\dfrac{1}{3}=\dfrac{4}{3}\\ \left(2x-\dfrac{9}{2}\right)=\dfrac{4}{3}\cdot\dfrac{3}{4}=1\\ 2x=1+\dfrac{9}{2}=\dfrac{11}{2}\\ x=\dfrac{11}{2}:2=\dfrac{11}{4}\)
DN
14 tháng 4 2018
a) 1/2 . x + 1/8 . x = 3/4
<=> ( 1/2 + 1/8 ) . x = 3/4
<=> ( 4/8 + 1/8 ) . x = 3/4
<=> 5/8 . x = 3/4
<=> x = 3/4 . 8/5
<=> x = 6/5
Vậy x = 6/5
b) ( 2x - 4,5 ) : 3/4 - 1/3 = 1
<=> ( 2x - 45/10 ) : 3/4 - 1/3 = 1
<=> ( 2x - 9/2 ) : 3/4 - 1/3 = 1
<=> ( 2x - 9/2 ) : 3/4 = 1 + 1/3
<=> ( 2x - 9/2 ) : 3/4 = 4/3
<=> 2x - 9/2 = 4/3 . 3/4
<=> 2x - 9/2 = 1
<=> 2x = 1 + 9/2
<=> 2x = 11/2
<=> x = 11/2 . 1/2
<=> x = 11/4
Vậy x = 11/4
\(4,5-2x.1\dfrac{4}{7}=\dfrac{11}{14}\)
<=>\(-\dfrac{22}{7}x=\)\(\dfrac{11}{14}-4,5\)
<=>\(-\dfrac{22}{7}x=-\dfrac{26}{7}\)
<=>\(x=-\dfrac{26}{7}:\left(-\dfrac{22}{7}\right)\)
<=>\(x=\dfrac{13}{11}\)
4,5 -2x.11/7=11/4
2x.11/7=4.5-11/4
2x.11/7=7/4
2x =7/4: 11/7
2x=49/44
x=49/44: 2
x=49/88