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6 tháng 8 2015

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31 tháng 1 2016

2(\(\frac{3}{4}\)-5x)=\(\frac{4}{5}\)-3x

=> \(\frac{6}{4}-10x=\frac{4}{5}-3x\)

=>\(-10x+3x=\frac{4}{5}-\frac{6}{4}\)

=> \(x=\frac{1}{10}\)

2 .

\(\frac{3}{2}-4\left(\frac{1}{4}-x\right)=\frac{2}{3}-7x\)

=>\(\frac{3}{2}-1+4x=\frac{2}{3}-7x\)

=>\(11x=\frac{1}{6}\)

=>x=\(\frac{1}{66}\)

3.

\(3\left(\frac{1}{2}-x\right)+\frac{1}{3}=\frac{7}{6}-x\)

=>\(\frac{3}{2}-3x+\frac{1}{3}=\frac{7}{6}-x\)

=>\(-2x=\frac{-2}{3}\)

=>\(\frac{1}{3}\)

4. câu 4 ko hiểu bạn ơi

 

6 tháng 8 2015

hj các cậu làm câu nào cx được hết á

6 tháng 8 2015

1)\(-\frac{3}{2}\left(\frac{4}{5}-\frac{2}{3}\right)+x=4\left(x-\frac{2}{3}\right)\)

\(\Leftrightarrow-\frac{3}{2}\cdot\frac{2}{15}+x=4x-\frac{8}{3}\)

\(\Leftrightarrow-\frac{1}{5}+x=4x-\frac{8}{3}\)

\(\Leftrightarrow x-4x=-\frac{8}{3}+\frac{1}{5}\)

\(\Leftrightarrow-3x=-\frac{37}{15}\)

\(\Leftrightarrow x=\frac{37}{45}\)

 

2)\(2\left(\frac{3}{2}-x\right)-\frac{1}{3}=7x-\frac{1}{4}\)

\(\Leftrightarrow3-2x-\frac{1}{3}=7x-\frac{1}{4}\)

\(\Leftrightarrow-2x-7x=-\frac{1}{4}-3+\frac{1}{3}\)

\(\Leftrightarrow-9x=-\frac{35}{12}\)

\(\Leftrightarrow x=\frac{35}{108}\)

 

3)\(\frac{1}{5}\left(-\frac{3}{5}10\right)+5x=x-\frac{2}{3}\)

\(\Leftrightarrow-\frac{6}{5}+5x=x-\frac{2}{3}\)

\(\Leftrightarrow5x-x=-\frac{2}{3}+\frac{6}{5}\)

\(\Leftrightarrow4x=\frac{8}{15}\)

\(\Leftrightarrow x=\frac{2}{15}\)

 

4)\(-\frac{3}{2}\left(5-\frac{1}{6}\right)+4\left(x-\frac{1}{2}\right)=1\)

\(\Leftrightarrow-\frac{15}{2}+\frac{1}{4}+4x-2=1\)

\(\Leftrightarrow4x=1+\frac{15}{2}-\frac{1}{4}+2\)

\(\Leftrightarrow4x=\frac{41}{4}\)

\(\Leftrightarrow x=\frac{41}{16}\)

6 tháng 8 2015

1,\(2\left(\frac{3}{4}-5x\right)=\frac{4}{5}-3x\)

\(\frac{6}{4}-10x=\frac{4}{5}-3x\)

\(\frac{6}{4}+\frac{4}{5}=7x\)

\(\frac{23}{10}=7x\)

\(\frac{23}{70}=x\)

2,\(\frac{3}{2}-4\left(\frac{1}{4}-x\right)=\frac{2}{3}-7x\)

\(\frac{3}{2}-1-4x=\frac{2}{3}-7x\)

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

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

\(\frac{1}{18}=x\)

3,\(3\left(\frac{1}{2}-x\right)+\frac{1}{3}=\frac{7}{6}-x\)

\(\frac{3}{2}-3x+\frac{1}{3}=\frac{7}{6}-x\)

\(\frac{3}{2}-\frac{7}{6}+\frac{1}{3}=2x\)

\(\frac{2}{3}=2x\)

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

4,mình không hiểu a ở đây là gì

 

 

 

11 tháng 3 2020

1) \(\frac{7}{8}x-5\left(x-9\right)=\frac{20x+1,5}{6}\)

<=> \(\frac{21x}{24}-\frac{100\left(x-9\right)}{24}=\frac{80x+6}{24}\)

<=> 21x - 100x + 900 = 80x + 6

<=> -79x - 80x = 6 - 900

<=> -159x = -894

<=> x = 258/53

Vậy S = {258/53}

2) \(\frac{\left(2x+1\right)^2}{5}-\frac{\left(x+1\right)^2}{3}=\frac{7x^2-14x-5}{15}\)

<=> \(\frac{3\left(4x^2+4x+1\right)}{15}-\frac{5\left(x^2+2x+1\right)}{15}=\frac{7x^2-14x-5}{15}\)

<=> 12x2 + 12x + 3 - 5x2 - 10x - 5 = 7x2 - 14x - 5

<=> 7x2 + 2x - 7x2 + 14x = -5 + 2

<=> 16x = 3

<=> x = 3/16

Vậy S  = {3/16}

11 tháng 3 2020

3) 4(3x - 2) - 3(x - 4) = 7x+  10

<=> 12x - 8 - 3x + 12 = 7x + 10

<=> 9x - 7x = 10 - 4

<=> 2x = 6

<=> x = 3

Vậy S = {3}

4) \(\frac{\left(x+10\right)\left(x+4\right)}{12}-\frac{\left(x+4\right)\left(2-x\right)}{4}=\frac{\left(x+10\right)\left(x-2\right)}{3}\)

<=> \(\frac{x^2+14x+40}{12}+\frac{3\left(x^2+2x-8\right)}{12}=\frac{4\left(x^2+8x-20\right)}{12}\)

<=> x2 + 14x + 40 + 3x2 + 6x - 24 = 4x2 + 32x - 80

<=> 4x2 + 20x - 4x2 - 32x = -80 - 16

<=> -12x = -96

<=> x = 8

Vậy S = {8}

24 tháng 7 2018

Giải:

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

\(\Leftrightarrow2x=\frac{1}{2}-\left(\frac{1}{5}-\frac{2}{3}\right)\)

\(\Leftrightarrow2x=\frac{1}{2}-\frac{-7}{15}\)

\(\Leftrightarrow2x=\frac{11}{15}\)

\(\Leftrightarrow x=\frac{11}{15}:2\)

\(\Leftrightarrow x=\frac{11}{30}\)

b) \(4\left(\frac{1}{3}-3\right)+\frac{1}{2}=\frac{5}{6}+x\)

\(\Leftrightarrow\frac{-61}{6}=\frac{5}{6}+x\)

\(\Leftrightarrow x=\frac{-61}{6}-\frac{5}{6}\)

\(\Leftrightarrow x=\frac{-66}{6}=-11\)

26 tháng 6 2018

a) Qui đồng rồi khử mẫu ta được:

   3(3x+2)-(3x+1)=2x.6+5.2

<=> 9x+6-3x-1 = 12x+10

<=> 9x-3x-12x  = 10-6+1

<=> -6x            = 5

<=> x               = -5/6

Vậy ....

b) ĐKXĐ: \(x\ne\pm2\)

Qui đồng rồi khử mẫu ta được:

   (x+1)(x+2)+(x-1)(x-2) = 2(x2+2)

<=> x2+3x+2+x2-3x+2 = 2x2+4

<=> x2+x2-2x2+3x-3x = 4-2-2

<=> 0x             = 0

<=> x vô số nghiệm

Vậy x vô số nghiệm với x khác 2 và x khác -2

c) \(\left(2x+3\right)\left(\frac{3x+7}{2-7x}+1\right)=\left(x-5\right)\left(\frac{3x+8}{2-7x}+1\right)\) (ĐKXĐ:x khắc 2/7)

\(\Leftrightarrow\left(2x+3\right)\left(\frac{3x+8}{2-7x}+1\right)-\left(x-5\right)\left(\frac{3x+8}{2-7x}+1\right)=0\)

\(\Leftrightarrow\left(\frac{3x+8}{2-7x}+1\right)\left[\left(2x+3\right)-\left(x-5\right)\right]=0\)

\(\Leftrightarrow\left(\frac{3x+8}{2-7x}+1\right)\left(x+8\right)=0\)

\(\Leftrightarrow\orbr{\begin{cases}\frac{3x+8}{2-7x}+1=0\\x+8=0\end{cases}}\Leftrightarrow\orbr{\begin{cases}\frac{3x+8}{2-7x}=-1\\x+8=0\end{cases}}\Leftrightarrow\orbr{\begin{cases}3x+8=-1\left(2-7x\right)\\x=0-8\end{cases}}\)

\(\Leftrightarrow\orbr{\begin{cases}3x+8=-2+7x\\x=-8\end{cases}\Leftrightarrow\orbr{\begin{cases}-4x=-10\\x=-8\end{cases}\Leftrightarrow}\orbr{\begin{cases}x=\frac{5}{2}\\x=-8\end{cases}}}\) (nhận)

Vậy ...... 

d) (x+1)2-4(x2-2x+1) = 0

<=> x2+2x+1-4x2+8x-4 = 0

<=> -3x2+10x-3 = 0

giải phương trình

khỏi chép lại đề ha

  • 2 - 4x - 5x + \(\frac{3}{2}\)= \(\frac{7}{4}\)

          \(\frac{7}{2}\)- 9x = \(\frac{7}{4}\)

           -9x = \(\frac{7}{2}-\frac{7}{4}\)

           -9x = \(\frac{7}{4}\)

            x = \(\frac{7}{4}:\left(-9\right)\)

            x = \(\frac{-7}{36}\)

  • 3 - 2x - \(\frac{1}{3}=7x-\frac{1}{4}\)

          -2x - 7x = \(\frac{-1}{4}-3+\frac{1}{3}\)

         -9x = \(\frac{-35}{12}\)

          x = \(\frac{-35}{12}:\left(-9\right)\)

          x = \(\frac{35}{108}\)

  • \(\frac{-15}{2}\)+ \(\frac{1}{4}\)+ 4x -2 = 1

            4x = 1 + \(\frac{15}{2}-\frac{1}{4}+2\)

            4x = \(\frac{41}{4}\)

            x = \(\frac{41}{4}:4\)

            x = \(\frac{41}{16}\)

8 tháng 1 2020

1.

\(\frac{2x+3}{4}-\frac{5x+3}{6}=\frac{3-4x}{12}\)

\(MC:12\)

Quy đồng :

\(\Rightarrow\frac{3.\left(2x+3\right)}{12}-\left(\frac{2.\left(5x+3\right)}{12}\right)=\frac{3x-4}{12}\)

\(\frac{6x+9}{12}-\left(\frac{10x+6}{12}\right)=\frac{3x-4}{12}\)

\(\Leftrightarrow6x+9-\left(10x+6\right)=3x-4\)

\(\Leftrightarrow6x+9-3x=-4-9+16\)

\(\Leftrightarrow-7x=3\)

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

2.\(\frac{3.\left(2x+1\right)}{4}-1=\frac{15x-1}{10}\)

\(MC:20\)

Quy đồng :

\(\frac{15.\left(2x+1\right)}{20}-\frac{20}{20}=\frac{2.\left(15x-1\right)}{20}\)

\(\Leftrightarrow15\left(2x+1\right)-20=2\left(15x-1\right)\)

\(\Leftrightarrow30x+15-20=15x-2\)

\(\Leftrightarrow15x=3\)

\(\Leftrightarrow x=\frac{3}{15}=\frac{1}{5}\)