\(2x+6=0\\ \Leftrightarrow2x=-6\\ \Leftrightarrow x=-3\)

\(4x+20=0\\ \Leftrightarrow4x=-20\\ \Leftrightarrow x=-5\)

\(2x-3=0\\ \Leftrightarrow2x=3\\ \Leftrightarrow x=\dfrac{3}{2}\)

\(15-7x=9-3x\\ \Leftrightarrow15-7x-9+3x=0\\ \Leftrightarrow6-4x=0\\ \Leftrightarrow-4x=-6\\ \Leftrightarrow x=\dfrac{3}{2}\)

\(3x-1=x+3\\ \Leftrightarrow3x-1-x-3=0\\ \Leftrightarrow2x-4=0\\ \Leftrightarrow2x=4\\ \Leftrightarrow x=2\)

(Lưu ý khi đăng câu hỏi: bạn phải phân chia các bài ra trước khi đăng ví dụ như bài trên bạn phải phân chia theo thứ tự câu a,b,c,...)

\(\frac{2x+3}{6}=\frac{7x-3}{15}\)

\(15\left(2x+3\right)=6\left(7x-3\right)\)

\(30x+45=42x-18\)

\(30x-42x=-18-45\)

\(-12x=-63\)

\(x=\frac{21}{4}\)

     \(\frac{2x+3}{6}=\frac{7x-3}{15}\)

\(\Rightarrow\frac{5.\left(2x+3\right)}{30}=\frac{2.\left(7x-3\right)}{30}\)

\(\Rightarrow5.\left(2x+3\right)=2.\left(7x-3\right)\)

\(\Rightarrow10x+15=14x-6\)

\(\Rightarrow10x-14x=-6-15\)

\(\Rightarrow-4x=-21\)

\(\Rightarrow x=-21:\left(-4\right)\)

\(\Rightarrow x=\frac{21}{4}\)

\(\frac{\left(2x+3\right)}{6}=\frac{\left(7x-3\right)}{15}\)

\(\Leftrightarrow\left(2x+3\right).15=\left(7x-3\right).6\)

\(\Leftrightarrow30x+45=42x-18\)

\(\Leftrightarrow42x-30x=45+18\)

\(\Leftrightarrow12x=63\)

\(\Leftrightarrow x=\frac{21}{4}=5,25\)

\(2x+\frac{3}{6}=7x-\frac{3}{15}\)

\(2x+\frac{1}{2}=7x-\frac{1}{5}\)

\(2x-7x=-\frac{1}{5}-\frac{1}{2}\)

\(-5x=-\frac{7}{10}\)

\(x=\frac{7}{50}\)

\(3x+\frac{3}{6}=7x+\frac{3}{15}\)

\(\Rightarrow4x=\frac{3}{10}\Rightarrow x=\frac{3}{40}\)

Ta co:

2x+3/6 = 7x + 3/15

=> 3/6 = 5x + 3/15

=> x = (3/6 - 3/15):5 = 3/50

1/ ĐKXĐ : \(x\ne1\)

\(\dfrac{7x-3}{x-1}=\dfrac{2}{3}\)

\(\Leftrightarrow21x-9=2x-2\)

\(\Leftrightarrow19x=7\Leftrightarrow x=\dfrac{7}{19}\left(tm\right)\)

Vậy...

b/ \(\dfrac{2\left(3-7x\right)}{1+x}=\dfrac{1}{2}\) ĐKXĐ : \(x\ne-1\)

\(\Leftrightarrow12-28x=1+x\)

\(\Leftrightarrow11=29x\Leftrightarrow x=\dfrac{11}{29}\) \(\left(tm\right)\)

Vậy....

c/ ĐKXĐ : \(x\ne0\)

\(\dfrac{x^2-6}{x}=x+\dfrac{3}{2}\)

\(\Leftrightarrow\dfrac{x^2-6}{x}=\dfrac{2x+3}{2}\)

\(\Leftrightarrow2x^2-12=2x^2+3x\)

\(\Leftrightarrow3x=-12\Leftrightarrow x=-4\) \(\left(tm\right)\)

Vậy...

4/ ĐKXĐ : \(x\ne-\dfrac{2}{3}\)

\(\dfrac{5}{3x+2}=2x-1\)

\(\Leftrightarrow\left(2x-1\right)\left(3x+2\right)=5\)

\(\Leftrightarrow6x^2+4x-3x-2=5\)

\(\Leftrightarrow6x^2+x-7=0\Leftrightarrow\left[{}\begin{matrix}x=-\dfrac{7}{6}\\x=1\end{matrix}\right.\)

Vậy....

5,6 Tương tự nhé !

1)ĐKXĐ: \(x\ne1\)

Ta có: \(\dfrac{7x-3}{x-1}=\dfrac{2}{3}\)

\(\Leftrightarrow3\left(7x-3\right)=2\left(x-1\right)\)

\(\Leftrightarrow21x-9=2x-2\)

\(\Leftrightarrow21x-9-2x+2=0\)

\(\Leftrightarrow19x-7=0\)

\(\Leftrightarrow19x=7\)

\(\Leftrightarrow x=\dfrac{7}{19}\)(nhận)

Vậy: \(S=\left\{\dfrac{7}{19}\right\}\)

2) ĐKXĐ: \(x\ne-1\)

Ta có: \(\dfrac{2\left(3-7x\right)}{1+x}=\dfrac{1}{2}\)

\(\Leftrightarrow4\left(3-7x\right)=x+1\)

\(\Leftrightarrow12-28x-x-1=0\)

\(\Leftrightarrow-29x+11=0\)

\(\Leftrightarrow-29x=-11\)

\(\Leftrightarrow x=\dfrac{11}{29}\)

Vậy: \(S=\left\{\dfrac{11}{29}\right\}\)

3) ĐKXĐ: \(x\ne0\)

Ta có: \(\dfrac{x^2-6}{x}=x+\dfrac{3}{2}\)

\(\Leftrightarrow\dfrac{x^2-6}{x}=\dfrac{2x+3}{2}\)

\(\Leftrightarrow2\left(x^2-6\right)=x\left(2x+3\right)\)

\(\Leftrightarrow2x^2-12=2x^2+6x\)

\(\Leftrightarrow2x^2-12-2x^2-6x=0\)

\(\Leftrightarrow-6x-12=0\)

\(\Leftrightarrow-6x=12\)

\(\Leftrightarrow x=-2\)

Vậy: S={-2}

câu f là 9+3x hay 9-3x vậy???

a) 

$2x+6=0$

$2x=-6$

$x=-3$

b) $4x+20=0$

$4x=-20$

$x=-5$

c) 

$2(x-1)=5x-7$

$2x-2=5x-7$

$3x=5$

$x=\frac{5}{3}$

d) $2x-3=0$

$2x=3$

$x=\frac{3}{2}$

e) 

$3x-1=x+3$

$2x=4$

$x=2$

f) 

$15-7x=9-3x$

$6=4x$

$x=\frac{3}{2}$

g) $x-3=18$

$x=18+3=21$

h) 

$2x+1=15-5x$

$7x=14$

$x=2$

c , d giải nốt:

c) 2x + 3/6 = 7x - 13/15

=> (2x + 3) . 15 = (7x - 13) x 6

=> 30x +45 = 42x - 78

=> 30x - 42x = -78 - 45

=> -12x = -123

=> x = 41/4

d) 2-x/4 = 3x - 1/ - 3

=> (2-x) . -3 = 4. (3x - 1)

=> -6 - (-3x) = 12x - 4

(-6) + 4 = 12x - - (-3x)

=> -2 = 9x

=> x = -2/9    

1.x=4

2.x=6

3.x=8