giúp mình với ạaaaaaaaa

`y10000`

`a )` $\text{ĐK : x ≠ + 3}$

$\text{Có : A = B}$

`=> \frac{x-1}{x-3}= \frac{x+1}{x+3}`

`<=> ( x - 1 ) . ( x + 3 ) = ( x + 1 ) . ( x - 3)`

`<=> x² + 3x - x - 3 = x² - 3x + x - 3`

`<=> x² + 2x - 3 = x² - 2x - 3`

`<=> x² + 2x - x² + 2x = - 3 + 3`

`<=> 4x = 0`

`<=> x = 0` $\text{(thỏa mãn)}$

`b )` $\text{ ĐK : x ≠ -3 , x ≠ -1}$

$\text{Có A = B}$

`=> \frac{x+1}{x+3}=\frac{2x+1}{3x+3}`

`<=> ( x +1)(3x+3)=(2x+1)(x+3)`

`<=> 3x² + 3x + 3x + 3 = 2x² + 6x + x + 3`

`<=> 3x² + 6x + 3 = 2x² + 7x + 3`

`<=> 3x² + 6x - 2x² - 7x = 3 - 3`

`<=> x² - x = 0`

`<=> x . ( x - 1 ) = 0`

`<=>` \(\left[ \begin{array}{l}x=0\\x-1=0\end{array} \right.\) 

`<=>` \(\left[ \begin{array}{l}x=0(TM)\\x=1(TM)\end{array} \right.\)