$\dfrac{3}{x + 7}$ + $\dfrac{2}{x - 7}$ = $\dfrac{5}{x² - 49}$
$\Leftrightarrow$ $\dfrac{3( x - 7 )}{( x - 7)(x + 7)}$ + $\dfrac{2(x + 7 )}{(x - 7)(x + 7}$ = $\dfrac{5}{x² - 49}$
$\Leftrightarrow$ $\text{3x - 21 + 2x + 14 = 5}$
$\Leftrightarrow$ $\text{3x + 2x = 21 - 14 + 5}$
$\Leftrightarrow$ $\text{5x = 12}$
$\Leftrightarrow$ $\text{x = $\dfrac{12}{5}$ ( TM )}$
$\text{ĐKXĐ: x $\ne$ $\pm$ 7 }$
@Meii

Đáp án+Giải thích các bước giải:

$\dfrac{3}{x+7}+$$\dfrac{2}{x-7}=$$\dfrac{5}{x^2-49}$       `(ĐKXĐ:x\ne±7)`

`<=>` $\dfrac{3}{x+7}+$$\dfrac{2}{x-7}=$$\dfrac{5}{(x+7)(x-7)}$

`<=>` $\dfrac{3(x-7)}{(x+7)(x-7)}+$$\dfrac{2(x+7)}{(x-7)(x+7)}=$$\dfrac{5}{(x+7)(x-7)}$

`<=>` $3(x-7)+2(x+7)=5$

`<=>` $3x-21+2x+14=5$

`<=>` $3x+2x=5+21-14$

`<=>` $5x=12$

`<=>` $x=$`12/5` (t.m)

Vậy `S={\frac{12}{5}}`