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BT
3
MV
5 tháng 5 2017
a)
\(2x-\dfrac{1}{4}=\dfrac{1}{2}\\ 2x=\dfrac{1}{2}+\dfrac{1}{4}\\ 2x=\dfrac{3}{4}\\ x=\dfrac{3}{4}:2\\ x=\dfrac{3}{8}\)
b)
\(\dfrac{-2}{3}\cdot x+\dfrac{1}{5}=\dfrac{3}{10}\\ \dfrac{-2}{3}x=\dfrac{3}{10}-\dfrac{1}{5}\\ \dfrac{-2}{3}x=\dfrac{1}{10}\\ x=\dfrac{1}{10}:\dfrac{-2}{3}\\ x=\dfrac{-3}{20}\)
AT
5 tháng 5 2017
a) \(2x-\dfrac{1}{4}=\dfrac{1}{2}\)
\(2x=\dfrac{1}{2}+\dfrac{1}{4}\)
\(2x=\dfrac{4}{8}+\dfrac{2}{8}=\dfrac{6}{8}=\dfrac{3}{4}\)
\(x=\dfrac{3}{4}:2=\dfrac{3}{4}.\dfrac{1}{2}=\dfrac{3}{8}\)
Vậy x = \(\dfrac{3}{8}\)
b) \(\dfrac{-2}{3}.x+\dfrac{1}{5}=\dfrac{3}{10}\)
\(\dfrac{-2}{3}.x=\dfrac{3}{10}-\dfrac{1}{5}\)
\(\dfrac{-2}{3}.x=\dfrac{3}{10}-\dfrac{2}{10}\)
\(\dfrac{-2}{3}.x=\dfrac{1}{10}\)
\(x=\dfrac{1}{10}:\dfrac{-2}{3}=\dfrac{1}{10}.\dfrac{3}{-2}\)
\(x=\dfrac{3}{-20}\)
Vậy x = \(\dfrac{3}{-20}\)
1 tháng 6 2017
a) \(\left|2x-1\right|=2\\ < =>\left\{{}\begin{matrix}2x-1=-2\\2x-1=2\end{matrix}\right.< =>\left\{{}\begin{matrix}x=-\dfrac{1}{2}\\x=\dfrac{3}{2}\end{matrix}\right.\)
b) \(\left(3\dfrac{1}{2}-2x\right).\dfrac{4}{9}=5\dfrac{1}{3}\\ < =>\left(\dfrac{7}{2}-2x\right).\dfrac{4}{9}=\dfrac{16}{3}\\ =>\dfrac{7}{2}-2x=\dfrac{\dfrac{16}{3}}{\dfrac{4}{9}}=12\\ =>2x=\dfrac{7}{2}-12=-\dfrac{17}{2}\\ =>x=\dfrac{\dfrac{-17}{2}}{2}=-\dfrac{17}{4}\)
DN
1 tháng 6 2017
a) |2x - 1| = 2
=> 2x - 1 = 2 => x = 1,5
hoặc 2x - 1 = -2 => x = -0,5
Vậy x = 1,5 hoặc x = -0,5
b) \(\left(3\dfrac{1}{2}-2x\right)\dfrac{4}{9}=5\dfrac{1}{3}\)
\(\left(\dfrac{7}{2}-2x\right)\dfrac{4}{9}=\dfrac{16}{3}\)
=> \(\dfrac{7}{2}-2x=\dfrac{16}{3}:\dfrac{4}{9}=12\)
=> \(2x=\dfrac{7}{2}-12=\dfrac{-17}{2}\)
=> \(x=\dfrac{-17}{2}:2=\dfrac{-17}{4}\)
Vậy \(x=\dfrac{-17}{4}\)
3 tháng 7 2022
a: \(\Leftrightarrow x^2=\dfrac{-5}{2}\cdot\dfrac{-10}{9}=\dfrac{50}{18}=\dfrac{25}{9}\)
=>x=5/3hoặc x=-5/3
c: \(\Leftrightarrow4\left(x-\dfrac{5}{8}\right)=\dfrac{1}{4}+\dfrac{3}{4}=1\)
=>x-5/8=1/4
hay x=2/8+5/8=7/8
d: \(\Leftrightarrow\left|x-3\right|=\dfrac{2}{5}+\dfrac{3}{5}=1\)
=>x-3=1 hoặc x-3=-1
=>x=4 hoặc x=2
e: =>1-1/2x=-3
=>1/2x=4
hay x=8
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, \(\left(4,5-200\%x\right).1\dfrac{4}{7}=\dfrac{11}{14}\\ < =>\left(4,5-2x\right).\dfrac{11}{7}=\dfrac{11}{4}\\ =>4,5-2x=\dfrac{11}{4}:\dfrac{11}{7}=\dfrac{7}{4}\\ =>2x=4,5-\dfrac{7}{4}=\dfrac{11}{4}\\ =>x=\dfrac{\dfrac{11}{4}}{2}=\dfrac{11}{8}\)
1 tháng 8 2019
a) \(\frac{3x-6}{x+4}=\frac{2\left(x+5\right)+\left(x-3\right)}{x-2}\)
\(\frac{3\left(x-2\right)}{x+4}=\frac{2\left(x+5\right)+x-3}{x-2}\)
\(\frac{3\left(x-4\right)}{x+4}=\frac{3x+7}{x-2}\)
\(3\left(x-2\right)\left(x-2\right)=\left(3x+7\right)\left(x+4\right)\)
\(3\left(x-2\right)^2=\left(3x+7\right)\left(x+4\right)\)
\(3x^2-12x+12=3x^2+12x+7x+28\)
\(3x^2-12x+12=3x^2+19x+28\)
\(-12x+12=19x+28\)
\(12=19x+28+12x\)
\(19x+28+12x=12\) (chuyển vế)
\(31x+28=12\)
\(31x=12-28\)
\(31x=-16\)
\(x=-\frac{16}{31}\)
\(\Rightarrow x=-\frac{16}{31}\)
TN
3 tháng 6 2017
\(a,\dfrac{2}{3}x-\dfrac{1}{2}=\dfrac{1}{10}\Leftrightarrow\dfrac{2}{3}x=\dfrac{1}{10}+\dfrac{1}{2}\Leftrightarrow\dfrac{2}{3}x=\dfrac{2}{3}\Leftrightarrow x=\dfrac{2}{3}:\dfrac{2}{3}=1\)\(b,5\dfrac{4}{7}:x=13\Leftrightarrow\dfrac{39}{7}:x=13\Leftrightarrow x=\dfrac{39}{7}:13=\dfrac{3}{7}\)\(c,\left(2\dfrac{4}{5}x-50\right):\dfrac{2}{3}=51\Leftrightarrow\left(\dfrac{14}{5}x-50\right).\dfrac{3}{2}=51\Leftrightarrow\dfrac{21}{5}x-75=51\Leftrightarrow\dfrac{21}{5}x=51+75=126\Leftrightarrow x=126:\dfrac{21}{5}=30\)
TN
3 tháng 6 2017
d,\(\left(x+\dfrac{1}{2}\right).\left(\dfrac{2}{3}-2x\right)=0\Leftrightarrow\left[{}\begin{matrix}x+\dfrac{1}{2}=0\\\dfrac{2}{3}-2x=0\end{matrix}\right.\left[{}\begin{matrix}x=\dfrac{-1}{2}\\2x=\dfrac{2}{3}\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{-1}{2}\\x=\dfrac{1}{3}\end{matrix}\right.\)
MV
23 tháng 4 2017
9) \(\dfrac{x}{4}=\dfrac{9}{x}\)
Theo định nghĩa về hai phân số bằng nhau, ta có:
\(4\cdot9=x^2\\ 36=x^2\Rightarrow\left[{}\begin{matrix}x=6\\x=-6\end{matrix}\right.\)
8)
\(x:\dfrac{5}{3}+\dfrac{1}{3}=-\dfrac{2}{5}\\ x:\dfrac{5}{3}=-\dfrac{2}{5}+\dfrac{1}{3}\\ x:\dfrac{5}{3}=-\dfrac{1}{15}\\ x=\dfrac{1}{15}\cdot\dfrac{5}{3}\\ x=\dfrac{1}{9}\)
7)
\(2x-16=40+x\\ 2x-x=40+16\\ x\left(2-1\right)=56\\ x=56\)
6)
\(1\dfrac{1}{2}+x=\dfrac{3}{2}-7\\ \dfrac{3}{2}+x=\dfrac{3}{2}-7\\ \dfrac{3}{2}-\dfrac{3}{2}=-7-x\\ -7-x=0\\ x=-7-0\\ x=-7\)
5)
\(3\dfrac{1}{2}-\dfrac{1}{2}x=\dfrac{2}{3}\\ \dfrac{7}{2}-\dfrac{1}{2}x=\dfrac{2}{3}\\ \dfrac{1}{2}x=\dfrac{7}{2}-\dfrac{2}{3}\\ \dfrac{1}{2}x=\dfrac{17}{6}\\ x=\dfrac{17}{6}:\dfrac{1}{2}\\ x=\dfrac{17}{3}\)
4)
\(x\cdot\left(x+1\right)=0\Rightarrow\left[{}\begin{matrix}x=0\\x+1=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=0\\x=-1\end{matrix}\right.\)
3)
\(\left(\dfrac{2x}{5}+2\right):\left(-4\right)=-1\dfrac{1}{2}\\ \left(\dfrac{2x}{5}+2\right):\left(-4\right)=-\dfrac{3}{2}\\ \dfrac{2x}{5}+2=-\dfrac{3}{2}\cdot\left(-4\right)\\ \dfrac{2x}{5}+2=6\\ \dfrac{2x}{5}=6-2\\ \dfrac{2x}{5}=4\\ 2x=4\cdot5\\ 2x=20\\ x=20:2\\ x=10\)
2)
\(\dfrac{1}{3}+\dfrac{1}{2}:x=-0,25\\ \dfrac{1}{3}+\dfrac{1}{2}:x=-\dfrac{1}{4}\\ \dfrac{1}{2}:x=-\dfrac{1}{4}-\dfrac{1}{3}\\ \dfrac{1}{2}:x=-\dfrac{7}{12}\\ x=\dfrac{1}{2}:-\dfrac{7}{12}\\ x=-\dfrac{6}{7}\)
1)
\(\dfrac{4}{3}+x=\dfrac{2}{15}\\ x=\dfrac{2}{15}-\dfrac{4}{3}x=-\dfrac{6}{5}\)
2 tháng 5 2017
a) \(\left(2x-3\right)\left(6-2x\right)=0\)
\(\circledast\)TH1: \(2x-3=0\\ 2x=0+3\\ 2x=3\\ x=\dfrac{3}{2}\)
\(\circledast\)TH2: \(6-2x=0\\ 2x=6-0\\ 2x=6\\ x=\dfrac{6}{2}=3\)
Vậy \(x\in\left\{\dfrac{3}{2};3\right\}\).
b) \(\dfrac{1}{3}x+\dfrac{2}{5}\left(x-1\right)=0\)
\(\dfrac{1}{3}x=0-\dfrac{2}{5}\left(x-1\right)\)
\(\dfrac{1}{3}x=-\dfrac{2}{5}\left(x-1\right)\)
\(-\dfrac{2}{5}-\dfrac{1}{3}=-x\left(x-1\right)\)
\(-\dfrac{11}{15}=-x\left(x-1\right)\)
\(\Rightarrow x=1.491631652\)
Vậy \(x=1.491631652\)
c) \(\left(3x-1\right)\left(-\dfrac{1}{2}x+5\right)=0\)
\(\circledast\)TH1: \(3x-1=0\\ 3x=0+1\\ 3x=1\\ x=\dfrac{1}{3}\)
\(\circledast\)TH2: \(-\dfrac{1}{2}x+5=0\\ -\dfrac{1}{2}x=0-5\\ -\dfrac{1}{2}x=-5\\ x=-5:-\dfrac{1}{2}\\ x=10\)
Vậy \(x\in\left\{\dfrac{1}{3};10\right\}\).
d) \(\dfrac{x}{5}=\dfrac{2}{3}\\ x=\dfrac{5\cdot2}{3}\\ x=\dfrac{10}{3}\)
Vậy \(x=\dfrac{10}{3}\).
e) \(\dfrac{x}{3}-\dfrac{1}{2}=\dfrac{1}{5}\\ \)
\(\dfrac{x}{3}=\dfrac{1}{5}+\dfrac{1}{2}\)
\(\dfrac{x}{3}=\dfrac{7}{10}\)
\(x=\dfrac{3\cdot7}{10}\)
\(x=\dfrac{21}{10}\)
Vậy \(x=\dfrac{21}{10}\).
f) \(\dfrac{x}{5}-\dfrac{1}{2}=\dfrac{6}{10}\)
\(\dfrac{x}{5}=\dfrac{6}{10}+\dfrac{1}{2}\)
\(\dfrac{x}{5}=\dfrac{11}{10}\)
\(x=\dfrac{5\cdot11}{10}\)
\(x=\dfrac{55}{10}=\dfrac{11}{2}\)
Vậy \(x=\dfrac{11}{2}\).
g) \(\dfrac{x+3}{15}=\dfrac{1}{3}\\ x+3=\dfrac{15}{3}=5\\ x=5-3\\ x=2\)
Vậy \(x=2\).
h) \(\dfrac{x-12}{4}=\dfrac{1}{2}\\ x-12=\dfrac{4}{2}=2\\ x=2+12\\ x=14\)
Vậy \(x=14\).
TL
2 tháng 5 2017
6. \(\dfrac{x}{4}=\dfrac{9}{x}\)
=>x2=4.9=36
=>x\(\in\)\(\left\{-6;6\right\}\)
NT
Nguyễn Thị Thương Hoài
Giáo viên
VIP
27 tháng 8 2023
\((\dfrac{2x}{5}+2):\left(-4\right)=-1\dfrac{1}{2}\)
(\(\dfrac{2x}{5}+2):\left(-4\right)=-\dfrac{3}{2}\)
\(\dfrac{2x}{5}=-\dfrac{3}{2}.\left(-4\right)\)
\(\dfrac{2x}{5}=6\)
\(\dfrac{2x}{5}=\dfrac{30}{5}\)
2x = 30
x = 30 : 2 = 15
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