Tính : $\dfrac{5}{x - 3}$ `-` $\dfrac{ 3 + 5x }{x^2 - 9 }$ `+` $\dfrac{2}{x + 3}$

Đáp án:

$\dfrac{2}{x-3}$

Giải thích các bước giải:

$\dfrac{5}{x-3}-\dfrac{3+5x}{x^2-9}+\dfrac{2}{x+3}$ `;(x!=±3)`

$=\dfrac{5\left(x+3\right)}{\left(x-3\right)\left(x+3\right)}-\dfrac{3+5x}{\left(x-3\right)\left(x+3\right)}+\dfrac{2\left(x-3\right)}{\left(x-3\right)\left(x+3\right)}$

$=\dfrac{5\left(x+3\right)-\left(3+5x\right)+2\left(x-3\right)}{\left(x-3\right)\left(x+3\right)}$

$=\dfrac{2x+6}{\left(x-3\right)\left(x+3\right)}$

$=\dfrac{2}{x-3}$