đg cần gấp

\(2.8:\left(\frac{1}{5}-3x\right)=1\frac{2}{5}\)

\(\frac{14}{5}:\left(\frac{1}{5}-3x\right)=\frac{7}{5}\)

\(\frac{1}{5}-3x=\frac{14}{5}:\frac{7}{5}\)

\(\frac{1}{5}-3x=2\)

\(3x=\frac{1}{5}-2\)

\(3x=-\frac{9}{5}\)

\(x=-\frac{3}{5}\)

\(2,8:\left(\frac{1}{5}-3x\right)=1\frac{2}{5}\Rightarrow\frac{14}{5}:\left(\frac{1}{5}-3x\right)=\frac{7}{5}\)

\(\Rightarrow\frac{1}{5}-3x=\frac{14}{5}:\frac{7}{5}\)

\(\Rightarrow\frac{1}{5}-3x=2\)

\(\Rightarrow\frac{1}{5}-2=3x\)

\(\Rightarrow3x=-\frac{9}{5}\)

\(\Rightarrow x=-\frac{9}{5}:3=-\frac{3}{5}\)

Ta có: \(2,8:\left(\frac{1}{5}-3x\right)=\frac{7}{5}\)

\(\Leftrightarrow\frac{14}{5}:\left(\frac{1}{5}-3x\right)=\frac{7}{5}\)

\(\Leftrightarrow\frac{1}{5}-3x=2\)

\(\Leftrightarrow3x=\frac{1}{5}-2=\frac{9}{5}\)

hay \(x=\frac{3}{5}\)

Vậy: \(x=\frac{3}{5}\)

\(\Rightarrow\) 1/5-3x = 2/8 : 7/5 = 5/28

\(\Rightarrow\) 3x = 1/5 - 5/28 = 3/140

\(\Rightarrow\) x = 3/140 : 3 = 1/140

\(2,8:\left(3.x-\frac{5}{8}\right)=2\frac{2}{5}\)

=>\(\frac{14}{5}:\left(3.x-\frac{5}{8}\right)=\frac{12}{5}\)

=>\(\frac{14}{5}:\frac{13}{5}=3.x-\frac{5}{8}\)

=>\(3.x-\frac{5}{8}=\frac{14}{13}\)

=>\(3.x=\frac{14}{13}+\frac{5}{8}\)

=>\(3.x=\frac{177}{104}\)

=>\(x=\frac{59}{104}\)

2,8 :( 3x -5/8)= 2/2/5

2,8:( 3x- 5,8)= 12/5

3x-5/8         = 2,8:12/5

3x -5/8        = 7/6

3x= 7/6 +5/8

3x= 43/ 24

x= 43/24 :3

x= 43/72

nha bn, mknghix vậy

\(2,8:\left(3x-\frac{5}{8}\right)=2\frac{2}{5}\)

\(\frac{14}{5}:\left(3x-\frac{5}{8}\right)=\frac{12}{5}\)

        \(\left(3x-\frac{5}{8}\right)\)\(=\frac{14}{5}:\frac{12}{5}\)

         \(\left(3x-\frac{5}{8}\right)\)\(=\frac{14}{5}.\frac{5}{12}\)

           \(3x-\frac{5}{8}\)   \(=\frac{7}{6}\)

          \(3x\)              \(=\frac{7}{6}+\frac{5}{8}\)

          \(3x\)               \(=\frac{28}{24}+\frac{15}{24}\)

          \(3x\)               \(=\frac{43}{24}\)

           \(x\)                \(=\frac{43}{24}:3\)

          \(x\)                  \(=\frac{43}{24}.\frac{1}{3}\)

         \(x\)                    \(=\frac{43}{72}\)

Vậy   \(x\)                     \(=\frac{43}{72}\)

CHÚC BẠN HỌC TỐT

a)-12.(8)

b) -0.6

a) \(-0,6x-\dfrac{7}{3}=5,4\Leftrightarrow-\dfrac{3}{5}x=5,4+\dfrac{7}{3}\Leftrightarrow x=\dfrac{116}{15}.\left(-\dfrac{5}{3}\right)=-\dfrac{116}{9}\).

b) \(2,8:\left(\dfrac{1}{5}-3x\right)=1\dfrac{2}{5}\Leftrightarrow\dfrac{1}{5}-3x=2,8:\dfrac{7}{5}\Leftrightarrow-3x=2-\dfrac{1}{5}\Leftrightarrow x=\dfrac{9}{5}:\left(-3\right)=-\dfrac{3}{5}\).

a.x : 0,15 = (2,8 + 0,38) : 0,75

   x : 0,15 =3,18 : 0,75

   x : 0,15 = 4.24

   x          = 4,24 . 0,15

   x          = 0.636

b.5/12 : x = (5/6 - 1/2) . 5/4

   5/12 : x = 1/3 . 5/4 

   5/12 : x = 5/12

            x = 5/12 : 5/12 

            x = 1

a) \(\left|2x\right|-\left|-2,5\right|=\left|-7,5\right|\)

\(\Leftrightarrow\left|2x\right|-2,5=7,5\)

\(\Leftrightarrow\left|2x\right|=10\)            

\(\Leftrightarrow\begin{cases}x\ge0\\2x=10\end{cases}\) hoặc \(\begin{cases}x< 0\\2x=-10\end{cases}\)

\(\Leftrightarrow\begin{cases}x\ge0\\x=5\left(tm\right)\end{cases}\) hoặc \(\begin{cases}x< 0\\x=-5\left(tm\right)\end{cases}\)

Vậy x={5;-5}

b)\(\left|3x\right|\cdot\left|-3,5\right|=\left|-2,8\right|\)

\(\Leftrightarrow\left|3x\right|\cdot3,5=2,8\)

\(\Leftrightarrow\left|3x\right|=\frac{4}{5}\)

\(\Leftrightarrow\begin{cases}x\ge0\\3x=\frac{4}{5}\end{cases}\) hoặc \(\begin{cases}x< 0\\3x=-\frac{4}{5}\end{cases}\)

\(\Leftrightarrow\begin{cases}x\ge0\\x=\frac{4}{15}\end{cases}\) hoặc \(\begin{cases}x< 0\\x=-\frac{4}{15}\end{cases}\)

Vậy x={4/15;-4/15}

c) \(\left(3x-5\right)\left(\frac{3}{2}x+2\right)\left(0,5x-10\right)=0\)

\(\Leftrightarrow\left[\begin{array}{nghiempt}3x-5=0\\\frac{3}{2}x+2=0\\0,5x-10=0\end{array}\right.\)\(\Leftrightarrow\left[\begin{array}{nghiempt}x=\frac{5}{3}\\x=-\frac{4}{3}\\x=20\end{array}\right.\)

a)|2x|-|-2,5|=|-7,5|

   |2x|-2,5=7,5

    |2x|=10

\(\Rightarrow\left[\begin{array}{nghiempt}2x=10\\2x=-10\end{array}\right.\)\(\Rightarrow\left[\begin{array}{nghiempt}x=5\\x=-5\end{array}\right.\)

                 Vậy x=5;-5

b)|3x|.|-3,5|=|-2,8|

    |3x|.3,5=2,8

    |3x|=0,8

\(\Rightarrow\left[\begin{array}{nghiempt}3x=0,8\\3x=-0,8\end{array}\right.\)\(\Rightarrow\left[\begin{array}{nghiempt}x=\frac{4}{15}\\x=-\frac{4}{15}\end{array}\right.\)

                 Vậy \(x=\frac{4}{15};-\frac{4}{15}\)

c, ( 3x - 5 ) . ( \(\frac{3}{2}x\) + 2 ) . ( 0,5x - 10 ) = 0 

    \(\left(3x^2+6x-\frac{15}{2}x-10\right)\left(0,5x-10\right)=0\)

      \(\left(3x^2-\frac{3}{2}x-10\right)\left(0,5x-10\right)=0\)

     \(1,5x^3-0,75x^2-5x-30x^2+15x+100=0\)

     \(1,5x^3-30,75x^2+10x+100=0\)

      \(1,5x^3-1,5x^2.20,5+10x+100=0\)

     \(1,5x^2.\left(x-20,5\right)+10.\left(x+10\right)=0\)

Đến đây thì mk .......