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a) 1/2x - 2/3x = 7/12
-1/6x = 7/12
x = \(\frac{7}{12}\div\frac{-1}{6}\)
x = -7/2
b) x: 12 = -2,5
x = -2,5*12
x = -30
c) 11/2x = 13/15
x = 13/15:11/2
x = 26/165
d) 3x/7 + 1 = (-1/28)*(-4)
3x/7 + 1 = 1/7
3x/7 = 1/7 - 1
3x/7 = -6/7
3x = -6
x= -6/3
x= -2
![](https://rs.olm.vn/images/avt/0.png?1311)
a) x(0.5 - 2/3 ) = 7/12
(-1/6)x = 7/12
x = 7/12 : (-1/6)
x =-7/2
b) x : 12 = -2,5
x= -2.5 * 12 =-30
c) x = 13/15 : 5,5
x =26/125
d) 3x/7 + 1 = -1/28 * (-4)
3x/7 + 1 =1/7
3x/7 = 1/7 -1
3x/7 =-6/7
3x =-6/7 * 7
3x = -6
x =-2
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![](https://rs.olm.vn/images/avt/0.png?1311)
1a)1+2+3+...+x=0
\(\frac{x.\left(x+1\right)}{2}\)=0
x.(x+1) =0:2
x.(x+1) =0
x.(x+1) =0.1
vây x=0
tich dung cho minh nha
a> x=13/12:2/3=13/8. vậy x=13/8
b>x=5/4 nhân 5/4=25/16. vậy...
c>x=7/4+1/2=9/4. vậy x=+-9/4
d>x=x=1-1/4=3/4. vậy...
a) \(0,5-\frac{2}{3}x=\frac{-7}{12}\)
\(\frac{1}{2}-\frac{2}{3}x=\frac{-7}{12}\)
\(\frac{2}{3}x=\frac{1}{2}-\frac{-7}{12}\)
\(\frac{2}{3}x=\frac{13}{12}\)
\(x=\frac{13}{12}:\frac{2}{3}\)
\(x=\frac{13}{8}\)
b) \(\frac{3}{4}-x:\frac{5}{4}=\frac{-1}{2}\)
\(x:\frac{5}{4}=\frac{3}{4}-\frac{-1}{2}\)
\(x:\frac{5}{4}=\frac{5}{4}\)
\(x=\frac{5}{4}.\frac{5}{4}\)
\(x=\frac{25}{16}\)
c) \(\left|x-\frac{1}{2}\right|-\frac{1}{4}=\frac{3}{2}\)
\(\left|x-\frac{1}{2}\right|=\frac{3}{2}+\frac{1}{4}\)
\(\left|x-\frac{1}{2}\right|=\frac{7}{4}\)
\(\Rightarrow\orbr{\begin{cases}x-\frac{1}{2}=\frac{7}{4}\\x-\frac{1}{2}=\frac{-7}{4}\end{cases}\Rightarrow\orbr{\begin{cases}x=\frac{9}{4}\\x=\frac{-5}{4}\end{cases}}}\)
Vậy x = 9/4 hoặc x = -5/4
d) \(\left|1-x\right|=\frac{1}{4}\)
\(\Rightarrow\orbr{\begin{cases}1-x=\frac{1}{4}\\1-x=\frac{-1}{4}\end{cases}\Rightarrow\orbr{\begin{cases}x=\frac{3}{4}\\x=\frac{5}{4}\end{cases}}}\)
Vậy x = 3/4 hoặc 5/4