Question

[Buddy]

Thực hiện các phép tính sau:

a) \(\dfrac{{2{x^2} - 1}}{{x - 2}} + \dfrac{{ - {x^2} - 3}}{{x - 2}}\)                       

b) \(\dfrac{x}{{x + y}} + \dfrac{y}{{x - y}}\)    

c) \(\dfrac{1}{{x - 1}} - \dfrac{2}{{{x^2} - 1}}\)

d) \(\dfrac{{x + 2}}{{{x^2} + xy}} - \dfrac{{y - 2}}{{xy + {y^2}}}\)                                  

e) \(\dfrac{1}{{2{x^2} - 3x}} - \dfrac{1}{{4{x^2} - 9}}\)                     

g) \(\dfrac{{2x}}{{9 - {x^2}}} + \dfrac{1}{{x - 3}} - \dfrac{1}{{x + 3}}\)   

Answer 1

[Nguyễn Lê Phước Thịnh]

a: \(=\dfrac{2x^2-1-x^2-3}{x-2}=\dfrac{x^2-4}{x-2}=x+2\)

b: \(=\dfrac{x\left(x-y\right)+y\left(x+y\right)}{\left(x+y\right)\left(x-y\right)}\)

\(=\dfrac{x^2-xy+xy+y^2}{x^2-y^2}=\dfrac{x^2+y^2}{x^2-y^2}\)

c: \(=\dfrac{x+1-2}{\left(x-1\right)\left(x+1\right)}=\dfrac{\left(x-1\right)}{\left(x-1\right)\left(x+1\right)}=\dfrac{1}{x+1}\)

d: \(=\dfrac{\left(x+2\right)\cdot y-x\left(y-2\right)}{xy\left(x+y\right)}\)

\(=\dfrac{2y+2x}{xy\left(x+y\right)}=\dfrac{2}{xy}\)

e: \(=\dfrac{1}{x\left(2x-3\right)}-\dfrac{1}{\left(2x-3\right)\left(2x+3\right)}\)

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

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