Giúp mình với ạ em cảm ơn

$\text{a) A = $\dfrac{x - 2}{x}$ Đkxđ: x $\neq$ 0}$

$\text{Có: x = 6 (t/m)}$

$\text{Thay x = 6 vào biểu thức A ta được:}$

$\text{A = $\dfrac{6 - 2}{6}$ }$

$\text{= $\dfrac{4}{6}$}$

$\text{= $\dfrac{2}{3}$}$

$\text{Vậy A = $\dfrac{2}{3}$ khi x = 6}$

$\text{b) B = $\dfrac{4x}{x + 1}$ - $\dfrac{x + 1}{x - 1}$ + $\dfrac{3x + 1}{x² - 1}$ Đkxđ: x $\neq$ ±1}$

$\text{= $\dfrac{4x(x - 1) - (x + 1)(x + 1) + (3x + 1)}{(x - 1)(x + 1)}$ }$

$\text{= $\dfrac{4x² - 4x - x² - 2x - 1 + 3x + 1}{(x - 1)(x + 1)}$ }$

$\text{= $\dfrac{3x² - 3x}{(x - 1)(x + 1)}$ }$

$\text{= $\dfrac{3x(x - 1)}{(x - 1)(x + 1)}$ }$

$\text{= $\dfrac{3x}{x + 1}$ }$

$\text{c) Có: P < 3 Đkxđ: x $\neq$ 0; x $\neq$ ±1}$

$\text{⇒ $\dfrac{x - 2}{x}$ . $\dfrac{3x}{x + 1}$ < 3}$

$\text{⇔ $\dfrac{3(x - 2)}{x + 1}$ - 3 < 0}$

$\text{⇔ $\dfrac{(3x - 6) - 3(x + 1)}{x + 1}$ < 0}$

$\text{⇔ $\dfrac{3x - 6 - 3x - 3}{x + 1}$ < 0}$

$\text{⇔ $\dfrac{-9}{x + 1}$ < 0}$

$\text{Mà -9 < 0}$

$\text{⇒ x + 1 > 0}$

$\text{⇔ x > -1}$

$\text{Kết hợp với đkxđ, x > -1; x $\neq$ 0; x $\neq$ 1 thì P < 3}$

$\textit{Ha1zzz}$