\(3\frac{1}{3}x+16\frac{3}{4}=-13,25\)

\(\frac{10}{3}x+\frac{67}{4}=\frac{-53}{4}\)

\(\frac{10}{3}x=-30\)

\(x=-9\)

\(3\frac{1}{3}x+16\frac{3}{4}=-13,25\)

\(\frac{10}{3}x+\frac{67}{4}=\frac{-53}{4}\)

\(\frac{10}{3}x=-30\)

\(x=-9\)

\(3\frac{1}{3}x+16\frac{3}{4}=-13,25\)

\(\frac{10}{3}x=-13,25-16\frac{3}{4}\)

\(\frac{10}{3}x=-30\)

\(x=-9\)

nhân chéo là đc:

3(x+2)=-4(x-5)

3x+6=-4x+20

3x+4x=20-6

7x     =14

 x      =2

Vậy x=2

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

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

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

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

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

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

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

Vậy .....................

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

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

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

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

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

\(x=-\frac{1}{4}\cdot2\)

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

Vậy .....

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

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

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

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

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

bài 1)

70:2=35(m)

Gọi a và b lần lượt là chiều rộng và chiều dài của miếng đất

Từ b/a = 4 /3 = > 3/a = 4 /b

= > 3/ a = 4/ b = 3 + 4/ a + b = 7/ 35 = 5 /3 a = 5

= > a = 3.5 = 15/ 4 b = 5

= > b = 5.4 = 20

Vậy diện tích miếng đất đó là:

15.20=300(m2)

2) Bài 138 (Sách bài tập - tập 1 - trang 33)

 bài 2 cậu vào cái ý là có 

\(\frac{x+3}{-4}=-\frac{9}{x+3}\)

\(\Leftrightarrow\left(x+3\right)\left(x+3\right)=-4\cdot\left(-9\right)\)

\(\Leftrightarrow\left(x+3\right)^2=36\)

\(\Leftrightarrow\orbr{\begin{cases}\left(x+3\right)^2=6^2\\\left(x+3\right)^2=\left(-6\right)^2\end{cases}}\)

\(\Leftrightarrow\orbr{\begin{cases}x+3=6\\x+3=-6\end{cases}}\)

\(\Leftrightarrow\orbr{\begin{cases}x=3\\x=-9\end{cases}}\)

Vậy ....

quy đồng

\(\left(x+3\right)^2=36\)

\(\left(x+3\right)^2-6^2=0\)

áp dụng định lí "  \(a^2-b^2=\left(a+b\right)\left(a-b\right)\) ta được

\(\left(x+3-6\right)\left(x+3+6\right)=0\)

\(x=3,x=-9\)

nhân chéo: 

(x+3)(x+3)=-4.(-9)

(x+3)^2   =36

Hai TH: 

TH1: x+3=6

=>   x=3

TH2: x+3=-6

=>  x=-9

Vậy x=3 hoặc x=-9

b) \(\left(2,4.x-36\right)\div1\frac{5}{7}=-1\)

\(\left(2,4.x-36\right)=-1.\frac{12}{7}\)

\(2,4.x-36=-\frac{12}{7}\)

\(2,4.x=-\frac{12}{7}+36\)

\(2,4.x=\frac{240}{7}\)

\(x=\frac{240}{7}\div2,4\)

\(x=\frac{100}{7}\)

a) \(\frac{3}{x-5}=\frac{-4}{x+2}\)

\(\Rightarrow3.\left(x+2\right)=-4.\left(x-5\right)\)

\(\Rightarrow3x+6=-4x+20\)

\(\Rightarrow7x=14\)

\(\Rightarrow x=2\)

Câu c tương tự nhé. 

a) \(\frac{3}{x-5}=\frac{-4}{x+2}\)(ĐKXĐ: \(x\ne5;x\ne-2\))
\(\Rightarrow3\left(x+2\right)=-4\left(x-5\right)\)
\(\Leftrightarrow3x+6=-4x+20\)
\(\Leftrightarrow7x=14\)
\(\Leftrightarrow x=2\)(thỏa mãn ĐKXĐ)
b) \(2,4x-36=-\frac{7}{12}\)
\(\Leftrightarrow2,4x=\frac{425}{12}\)
\(\Leftrightarrow x=\frac{2125}{144}\)
c) \(\left(\frac{19}{5}-2x\right).\frac{4}{3}=\frac{40}{7}\)
\(\Leftrightarrow\frac{19}{5}-2x=\frac{30}{7}\)
\(\Leftrightarrow2x=-\frac{17}{35}\)
\(\Leftrightarrow x=-\frac{17}{70}\)
 

= 10/3.x+ 67/4=-53/4

   10/3.x=-53/4-67/4

   10/3.x=-30

   x=-30:10/3

   x=-9

\(M=\frac{\left(\frac{3}{10}-\frac{4}{15}-\frac{7}{20}\right).\frac{5}{19}}{\left(\frac{1}{17}+\frac{1}{7}-\frac{-3}{35}\right).\frac{-4}{3}}\)

\(M=\frac{\left(\frac{1}{30}-\frac{7}{20}\right).\frac{5}{19}}{\left(\frac{24}{119}+\frac{3}{35}\right).\frac{-4}{3}}\)

\(M=\frac{\frac{-19}{60}.\frac{5}{19}}{\frac{171}{595}.\frac{-4}{3}}\)

\(M=\frac{-1}{12}:\frac{-228}{595}\)

\(M=\frac{595}{2736}\)

Ta có: 

\(M=\frac{\left(\frac{3}{10}-\frac{4}{15}-\frac{7}{20}\right)\times\frac{5}{19}}{\left(\frac{1}{17}+\frac{1}{7}-\frac{-3}{35}\right)\times\frac{-4}{3}}\)

\(M=\frac{\left(\frac{1}{30}-\frac{7}{20}\right)\times\frac{5}{19}}{\left(\frac{24}{119}+\frac{3}{35}\right)\times\frac{-4}{3}}\)

\(M=\frac{\frac{-19}{60}\times\frac{5}{19}}{\frac{171}{595}\times\frac{-4}{3}}\)

\(M=\frac{-1}{12}\div\frac{-228}{595}\)

\(M=\frac{595}{2736}\)

Vậy \(M=\frac{595}{2736}\)