mai mình đi học cô kiểm tra nên ai đó giúp mk vs

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

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

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

\(3\left(x-2\right)\left(x-2\right)=\left(3x+7\right)\left(x+4\right)\)

\(3\left(x-2\right)^2=\left(3x+7\right)\left(x+4\right)\)

\(3x^2-12x+12=3x^2+12x+7x+28\)

\(3x^2-12x+12=3x^2+19x+28\)

\(-12x+12=19x+28\)

\(12=19x+28+12x\)

\(19x+28+12x=12\) (chuyển vế)

\(31x+28=12\)

\(31x=12-28\)

\(31x=-16\)

\(x=-\frac{16}{31}\)

\(\Rightarrow x=-\frac{16}{31}\)

(2/3×x-1/3)=2/3+1/3

(2/3×x-1/3)=3/3

2/3×x=3/3+1/3

2/3×x=4/3

x=4/3:3/2

x=4/3×2/3

x=8/9

Cảm ơn mn lần nx ạ

\(\Rightarrow2.\left(\frac{1}{2.4}+\frac{1}{4.6}+\frac{1}{6.8}+...+\frac{1}{\left(2x-2\right).2x}\right)=\frac{1}{8}.2\).2

\(\Rightarrow\frac{2}{2.4}+\frac{2}{4.6}+...\frac{2}{\left(2x-2\right).2x}=\frac{1}{4}\)

\(\Rightarrow\frac{1}{2}-\frac{1}{4}+\frac{1}{4}-\frac{1}{6}+...+\frac{1}{2x-2}-\frac{1}{2x}=\frac{1}{4}\)

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

\(\Rightarrow\frac{1}{2x}=\frac{1}{4}\Rightarrow\frac{1}{2x}=\frac{1}{2.2}\)

\(\Rightarrow x=2\)

Đề có sai ko bn ?

Dấu " . " k p dấu " , "

a) \(\frac{91}{1\cdot4}+\frac{91}{4\cdot7}+\frac{91}{7\cdot10}+...+\frac{91}{88\cdot99}\)

* Bài đúng k z ???

b) \(5\frac{1}{7}\left(3\frac{2}{3}+4\frac{1}{7}\right)=\frac{36}{7}\cdot\left(\frac{11}{3}+\frac{29}{7}\right)\)

\(=\frac{36}{7}\cdot\frac{164}{21}=\frac{1968}{49}\)

1/2 : 2x = -1/3

         2x = 1/2 : (-1/3)

         2x = 1/2 . (-3)

         2x = -3/2

           x = -3/2 : 2

           x = -3/2 . 1/2

           x = -3/4

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

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

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

\(\Rightarrow3.2=\left(-1\right).x\)

\(\Rightarrow6=\left(-1\right).x\)

\(\Rightarrow x=6:\left(-1\right)\)

\(\Rightarrow x=-6\)

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

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

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

\(\Rightarrow\hept{\begin{cases}x-1=2\\2=y\end{cases}\Rightarrow}\hept{\begin{cases}x=3\\y=2\end{cases}}\)

\(b,\frac{3}{x}+\frac{4}{3}=\frac{5}{6}\)

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

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

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

\(\Rightarrow x\cdot(-3)=18\Rightarrow x=-6\)

\(\frac{4}{5}\)và \(\frac{-8}{-10}\)

\(\frac{-20}{24}\)và \(\frac{-5}{6}\)

\(\frac{7}{3}\)và \(\frac{-14}{-6}\)