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

b)\(\frac{4}{5}\cdot x=\frac{4}{7}\Rightarrow x=\frac{4}{7}:\frac{4}{5}\)\(\Rightarrow x=\frac{5}{7}\)

c) \(8x=7,8x+25\Rightarrow8x-7,8x=25\)\(\Rightarrow0,2x=25\Rightarrow x=\frac{25}{0,2}\Rightarrow x=125\)

x = 2 hoặc = 6

Cách làm:

x² - 8x + 12 = 0

x² - 6x - 2x + 12 = 0

( x² - 6x ) - ( 6x - 12 ) = 0

x . ( x - 2 ) - 6 . ( x - 2 ) = 0

( x - 2 ) . ( x - 6 ) = 0

\(\Rightarrow\hept{\begin{cases}x-2=0\\x-6=0\end{cases}}\hept{\begin{cases}x=2\\x=6\end{cases}}\)

x²-8x+12=0

<=> x²-6x-2x+12=0

<=> (x²-2x)-(6x-12)=0

<=> x.(x-2)-6.(x-2)=0

<=> (x-2)(x-6)=0

<=>\(\orbr{\begin{cases}x-2=0\\x-6=0\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=2\\x=6\end{cases}}\)

\(=x^2-2x-6x+12\)

\(=x\left(x-2\right)-6\left(x-2\right)\)

\(=\left(x-2\right)\left(x-6\right)\)

8x=7,8x+25

8x-7,8x=25

0,2x=25

1/5x=25

x=25:1/5

x=25.5

x=125

là 125

8x- 7,8x = 25

x . 0,2 = 25

x = 25: 0,2

x=125

8x=7,8.x+25

8x-7,8x=25

0,2x=25

x=25:0,2

x = 125

\(7,8.x+25=8x\)

\(\Rightarrow8x-7,8x=25\)

\(\Rightarrow0,2x=25\Rightarrow x=125\)

Vậy x= 125

đề bài hỏi j zậy

thiếu đề 99.999999.....%

8x  = 7,8 .x+ 25

8x - 7,8 .x = 25

0,2 x = 25

     x = 25 : 0,2

     x = 125

x=125

chậm quá mấy Thánh

x=125

x=125

8x=7,8x+25

8x-7,8x=25

0,2x=25

x=25:0,2

x=125

\(\Leftrightarrow0,2x=25\)

\(\Leftrightarrow x=125\)

8x=1,8x + 25

8x - 7,8x =25

0,2x=25

 x = 25: 0,2

x = 125

X= 125

8x-7,8x=25

0,2x=25

x=25:0,2

x=125