Question

Answer 1

a) Thay x = \(\dfrac{-1}{2}\), ta có:

\(\dfrac{6}{-\dfrac{1}{2}+2}\) ⇔ \(\dfrac{6}{-\dfrac{3}{2}}\)⇔ 6.\(\dfrac{-2}{3}\)⇔ \(-4\) 

Vậy, khi thay x = \(\dfrac{-1}{2}\)thì biểu thức A có giá trị là \(-4\)

Answer 2

b) \(\dfrac{x}{x^2-4}\) - \(\dfrac{2}{x-2}\) + \(\dfrac{1}{x+2}\)

⇔ \(\dfrac{x}{\left(x-2\right)\left(x+2\right)}\) - \(\dfrac{2\left(x+2\right)}{\left(x-2\right)\left(x+2\right)}\)+ \(\dfrac{1}{\left(x-2\right)\left(x+2\right)}\)  

⇔ \(\dfrac{x-2\left(x+2\right)+1\left(x-2\right)}{\left(x-2\right)\left(x+2\right)}\)

⇔ \(\dfrac{x-2x-4+x-2}{\left(x-2\right)\left(x+2\right)}\)

⇔ \(\dfrac{-6}{\left(x-2\right)\left(x+2\right)}\)