Al là 3 nha
a)\(\dfrac{7}{x}\)-\(\dfrac{x}{x+6}\)+\(\dfrac{36}{x^2+6x}\)
b)\(\dfrac{1}{x^2-x+1}\)+1-\(\dfrac{x^2+2}{x^3+1}\)
c)\(\dfrac{x}{x^2-4}\)+\(\dfrac{2}{2-x}\)+\(\dfrac{1}{x+2}\)
\(\dfrac{-x^2}{x-1}\)+\(\dfrac{x^3-x}{x^3+1}\).(\(\dfrac{x}{x^2-2x+1}-\dfrac{1}{x^2-1}\))