a) \(\dfrac{x}{12}=\dfrac{6}{9}\)

\(\Rightarrow x=\dfrac{12\cdot6}{9}=8\)

b) \(\dfrac{9}{15}=x+\dfrac{11}{35}\)

\(\Rightarrow x=\dfrac{9}{15}-\dfrac{11}{35}\)

\(\Rightarrow x=\dfrac{2}{7}\)

c) \(x+\dfrac{6}{5}=\dfrac{x}{2}\)

\(\Rightarrow2\left(x+\dfrac{6}{5}\right)=x\)

\(\Rightarrow2x+\dfrac{12}{5}=x\)

\(\Rightarrow2x-x=-\dfrac{12}{5}\)

\(\Rightarrow x=-\dfrac{12}{5}\)

\(a,\dfrac{x}{12}=\dfrac{6}{9}\\ \Leftrightarrow x=12\cdot\dfrac{6}{9}\\ \Leftrightarrow x=8\\ b,\dfrac{9}{15}=x+\dfrac{11}{35}\\ \Leftrightarrow x=\dfrac{9}{15}-\dfrac{11}{35}\\ \Leftrightarrow x=\dfrac{2}{7}\\ c,x+\dfrac{6}{5}=\dfrac{x}{2}\\ \Leftrightarrow\dfrac{x}{2}=-\dfrac{6}{5}\\ \Leftrightarrow x=-\dfrac{12}{5}\)

a) 8

b) 2/7

c) -12/5

Bài làm

( 3 + 6 + x ) . 9 = ( 2 - x ) . 2

27 + 54 + 9x = 4 - 2x

9x + 2x = 4 - 27 - 54

11x = -77

x = -7

Vậy x = -7

b) ( 6 - x ) . 3 = ( 9 + x ) . 3

18 - 3x = 27 + 3x

-3x - 3x = 27 - 18

-6x = 9

x = 9/-6

x = -3/2

Vậy x = -3/2

a,\(\text{(3+6+x) . 9 = (2-x).2}\)

\(27+54+9x=4-2x\)

\(9x+2x=4-54-27\)

\(11x=-77\)

\(\Rightarrow x=-7\)

b, \(\text{(6-x) . 3 = (9+x) . 3}\)

\(18-3x=27+3x\)

\(-3x-3x=27-18\)

\(-6x=9\)

\(\Rightarrow x=\frac{9}{-6}\)

học tốt

\(\left(3+6+x\right)9=\left(2-x\right)2\)

\(27+54+9x=4-2x\)

\(27+54+9x-4+2x=0\)

\(77+11x=0\)

\(11x=-77\)

\(x=-7\)

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

\(18-3x=27+3x\)

\(18-3x-27-3x=0\)

\(-9-6x=0\)

\(6x=-9\)

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

X + 5/9 = 4/3   

X = 4/3 - 5/9

X = 7/9 

X - 4/9 = 1/2       

X = 1/2 + 4/9

X =  17/18 

6/13 + X = 7/6 

X = 7/6 - 6/13

X = 55/78

13/5 - X = 5/6   
X = 13/5 - 5/6

X= 53/30

X + 5/9 = 4/3 

x           = 4/3 - 5/9

x           =   7/9

  X - 4/9 = 1/2   

  x          = 1/2 + 4/9 

  x          =   17/18        

6/13 + X = 7/6     

            x = 7/6 - 6/13 

            x -  55/78

13/5 - X = 5/6 

          x  = 13/5 - 5/6

          x  =   53/30   

hc ngiu thế eim anh lười giải lắm =))))

\(\Leftrightarrow x^2-36-x^2+12x-9=9\)

\(\Leftrightarrow12x=54\)

hay x=9/2

Ta có

( x   –   6 ) ( x   +   6 )   –   ( x   +   3 ) 2   =   9     ⇔   x 2   –   36   –   ( x 2   +   6 x   +   9 )   =   9     ⇔   x 2   –   36   –   x 2   –   6 x   –   9   –   9   =   0

ó - 6x – 54 = 0 ó 6x = -54 ó x = -9

Vậy x = -9

Đáp án cần chọn là: A

\(a,\Leftrightarrow x^2-x-x^2+4x-4=2\\ \Leftrightarrow3x=6\Leftrightarrow x=2\\ b,\Leftrightarrow\left(x-3\right)\left(x+3\right)-\left(x-3\right)\left(6-x\right)=0\\ \Leftrightarrow\left(x-3\right)\left(x+3-6+x\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}x=3\\x=\dfrac{3}{2}\end{matrix}\right.\\ c,\Leftrightarrow x^2+2x-3x-6=0\\ \Leftrightarrow\left(x+2\right)\left(x-3\right)=0\Leftrightarrow\left[{}\begin{matrix}x=-2\\x=3\end{matrix}\right.\)

(x + 6)(x + 3)(x + 9)(x + 2) = 5x² 

<=> (x² + 9x + 18).(x² + 11x + 18) = 5x² 

<=> (x² + 10x + 18 - x)(x² + 10x + 18 + x) = 5x² 

<=> (x² + 10x + 18)² - x² = 5x² 

<=> (x² + 10x + 18)² = 6x²

<=> \(\left[{}\begin{matrix}x^2+10x+18=\sqrt{6}x\\x^2+10x+18=-\sqrt{6}x\end{matrix}\right.\)

Với \(x^2+10x+18=\sqrt{6}x\Leftrightarrow x^2+\left(10-\sqrt{6}\right)x+18=0\)

\(\Delta=\left(10-\sqrt{6}\right)^2-72=34-20\sqrt{6}< 0\) 

=> Phương trình vô nghiệm

Với \(x^2+10x+18=-\sqrt{6}x\Leftrightarrow x^2+\left(10+\sqrt{6}\right)x+18=0\)

\(\Delta=\left(10+\sqrt{6}\right)^2-72=34+20\sqrt{6}\) > 0

Phương trình có 2 nghiệm \(x=\dfrac{-10-\sqrt{6}\pm\sqrt{34+20\sqrt{6}}}{2}\)

\(\left(x+6\right)\left(x+3\right)\left(x+9\right)\left(x+2\right)=5x^2\)

\(\Leftrightarrow\left(x^2+3x+6x+18\right)\left(x^2+2x+9x+18\right)=5x^2\)

\(\Leftrightarrow\left(x^2+9x+18\right)\left(x^2+11x+18\right)=5x^2\)

\(\Leftrightarrow x^4+11x^3+18x^2+9x^3+99x^2+162x+18x^2+198x+324=5x^2\)

\(\Leftrightarrow x^4+20x^3+135x^2+360x+324=5x^2\)

\(\Leftrightarrow x^4+20x^3+130x^2+360x+324=0\)

\(\Leftrightarrow x\in\varnothing\)