`@` `\text {Ans}`

`\downarrow`

`a)`

`3x ( 12x - 4 ) - 9x( 4x - 3 ) = 30`

`=> 3x (12x-4) - 3*3x (4x - 3) = 30`

`=> 3x [12x - 4 - 3(4x-3)] = 30`

`=> 3x (12x - 4 - 12x + 9) = 30`

`=> 3x (-4+9)=30`

`=> 3x*5=30`

`=> 3x=6`

`=> x=2`

Vậy, `x=2`

`b)`

`x( 5 - 2x) + 2x( x - 1)`

`=> x(5-2x) + 2x^2 - 2x=15`

`=> 5x - 2x^2 + 2x^2 - 2x =15`

`=> 3x = 15`

`=> x=5`

Vậy, `x=5.`

a: =>36x^2-12x-36x^2+27x=30

=>15x=30

=>x=2

b: =>5x-2x^2+2x^2-2x=15

=>3x=15

=>x=5

C. 4,47

b) Ta có: \(x-43=\left(57-x\right)-50\)

\(\Leftrightarrow x-43=57-x-50\)

\(\Leftrightarrow x+x=7+43\)

\(\Leftrightarrow2x=50\)

hay x=25

Vậy: x=25

c) Ta có: (x-2)(8-x)=0

\(\Leftrightarrow\left[{}\begin{matrix}x-2=0\\8-x=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=2\\x=8\end{matrix}\right.\)

Vậy: \(x\in\left\{2;8\right\}\)

x = 4 giờ 15 phút:3

x = 1 giờ 25 phút

x  =4 giờ 15 phút : 3

x = 1 giờ 25 phút

a) \(x+\dfrac{4}{15}=\dfrac{4}{12}\)

\(x=\dfrac{4}{12}-\dfrac{4}{15}\)

\(x=\dfrac{20}{60}-\dfrac{16}{60}\)

\(x=\dfrac{1}{15}\)

b) \(x-\dfrac{5}{8}=1\dfrac{2}{3}\)

\(x-\dfrac{5}{8}=\dfrac{5}{3}\)

\(x=\dfrac{5}{3}+\dfrac{5}{8}\)

\(x=\dfrac{40}{24}+\dfrac{15}{24}\)

\(x=\dfrac{55}{24}\)

a)(x+3)2-x2+15=2x+6-2x+15=1

                        =21=1

Bạn chép sai đầu bài à

x2 là x^2 à

a) \(\dfrac{x.2}{-15}=\dfrac{-5}{3}\)

\(\dfrac{x.2}{-15}=\dfrac{25}{-15}\)

x.2=25

x=12,5

b) \(\dfrac{x-1}{-12}=\dfrac{-3}{x-1}\)

(x-1)²=-3.(-12)

(x-1)²=36 

⇒(x-1)²\(\Rightarrow\left[{}\begin{matrix}x-1=6\\x-1=-6\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=7\\x=-5\end{matrix}\right.\)

fffffff