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

bai nhiu qua troi

tự làm đi

\(\left(-3x-2\right)^2+\left(3x+5\right)\left(5-3x\right)=-7\)

\(\Leftrightarrow9x^2+12x+4+15x-9x^2+25-15x=-7\)

\(\Leftrightarrow12x+36=0\Leftrightarrow x=-3\)

\(\left(x+2\right)\left(x^2+2x+2\right)-x\left(x-8\right)^2=\left(4x-3\right)\left(4x+3\right)\)

\(\Leftrightarrow x^3+2x^2+2x+2x^2+4x+4-x\left(x^2-16x+64\right)=16x^2-9\)

\(\Leftrightarrow x^3+4x^2+6x+4-x^3+16x^2-64=16x^2-9\)

\(\Leftrightarrow4x^2+6x-51=0\)

\(\cdot\Delta=6^2-4.4.\left(-51\right)=852\)

Vậy pt có 2 nghiệm phân biệt

\(x_1=\frac{-6+\sqrt{852}}{8}\);\(x_2=\frac{-6-\sqrt{852}}{8}\)

a) \(0,5x-\frac{2}{3}x=\frac{7}{12}\)

\(\frac{1}{2}x-\frac{2}{3}x=\frac{7}{12}\)

\(\Rightarrow x\left(\frac{1}{2}-\frac{2}{3}\right)=\frac{7}{12}\)

\(x.\frac{-1}{6}=\frac{7}{12}\)

\(x=\frac{7}{12}:\frac{-1}{6}\)

\(x=\frac{-7}{2}\)

b) \(x:4\frac{1}{3}=-2,5\)

\(x:\frac{13}{3}=\frac{-5}{2}\)

\(x=\frac{-5}{2}.\frac{13}{3}\)

\(x=\frac{-65}{6}\)

c) \(5,5x=\frac{13}{15}=\frac{11}{2}x=\frac{13}{5}\)

\(x=\frac{13}{5}:\frac{11}{2}\)

\(x=\frac{26}{55}\)

d) \(\left(\frac{3x}{7}+1\right):\left(-4\right)=\frac{-1}{28}\)

\(\frac{3x}{7}+1=\frac{-1}{28}.\left(-4\right)\)

\(\frac{3x}{7}+1=\frac{1}{7}\)

\(\frac{3x}{7}=\frac{1}{7}-1\)

\(\frac{3x}{7}=\frac{-6}{7}\)

\(\frac{3x}{7}=\frac{-6}{7}\Rightarrow\frac{3.\left(-2\right)}{7}=\frac{-6}{7}\)

Vậy x = -2

\(0,5x-\frac{2}{3}x=\frac{7}{12}\)\(\)

\(\frac{1}{2}x-\frac{2}{3}x=\frac{7}{12}\)

\(x.\left(\frac{1}{2}-\frac{2}{3}\right)=\frac{7}{12}\)

\(x.\frac{-1}{6}=\frac{7}{12}\)

\(x=\frac{7}{12}:\frac{-1}{6}\)

\(x=3,5\)

3x(x-1)=1-x

<=> 3x(x-1) +x-1=0

<=> (x-1)(3x+1)=0

\(\Rightarrow\orbr{\begin{cases}x-1=0\\3x+1=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=1\\x=-\frac{1}{3}\end{cases}}}\)

Vậy...

Từ biểu thức, ta suy ra:

3x²-3x=1-x

<=>3x²-3x-1+x=0

<=>3x²-2x-1=0

<=>(3x²-3x)+(x-1)=0

<=>3x(x-1)+(x-1)=0

<=>(3x+1)(x-1)=0

<=>\(\orbr{\begin{cases}x=\frac{-1}{3}\\1\end{cases}}\)

Vậy phương trình có tập nghiệm S={-1/3;1}

<=>3x²-3x=1-x

<=>3x²-2x-1=0

<=>(x-1)(x-\(\frac{1}{3}\))=0

<=>\(\orbr{\begin{cases}x=1\\x=\frac{1}{3}\end{cases}}\)

1)\(25x+3\left(4-6x\right)=50\)

\(25x+12-18x=50\)

\(7x+12=50\)

\(7x=38\)

\(x=\frac{38}{7}\)

2)\(4\left(2x+3\right)+2\left(3x+1\right)=120\)

\(8x+12+6x+2=120\)

\(14x+14=120\)

\(14x=106\)

\(x=\frac{53}{7}\)

3)\(2\left(3x+2\right)+3\left(4x+1\right)=200\)

\(6x+4+12x+3=200\)

\(18x+7=200\)

\(18x=193\)

\(x=\frac{193}{18}\)

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

a,  \(0,5x-\frac{2}{3}x=\frac{7}{12}\)

=> \(x\left(0,5-\frac{2}{3}\right)=\frac{7}{12}\)

=>\(\frac{-1}{6}x=\frac{7}{12}\)=> \(x=\frac{7}{12}:\frac{-1}{6}=\frac{-7}{2}\)

b,  \(x:\frac{13}{3}=-2,5\)

=>\(x=\left(-2,5\right):\frac{13}{3}=\frac{-7,5}{13}\)

c,   \(5,5x=\frac{13}{15}\)

=>\(x=\frac{13}{15}:5,5=\frac{13}{82,5}\)

d,  \(\left(\frac{3x}{7}+1\right):\left(-4\right)=\frac{-1}{28}\)

=>\(\left(\frac{3x}{7}+1\right)=\frac{-1}{28}:\left(-4\right)=\frac{1}{7}\)

=>\(\frac{3x}{7}=\frac{1}{7}-1=\frac{-6}{7}\)

=>\(3x=-6\)

=> \(x=\left(-6\right):3=-3\)