Question

[nguyễn thị như ngọc]

giải giúp mình bài 21,22 với 

Answer 1

[Nguyễn Lê Phước Thịnh]

Bài 22:

Ta có: \(P=\left(\dfrac{x}{y^2+xy}-\dfrac{x-y}{x^2+xy}\right):\left(\dfrac{y^2}{x^3-xy^2}+\dfrac{1}{x+y}\right):\dfrac{x}{y}\)

\(=\left(\dfrac{x}{y\left(x+y\right)}-\dfrac{x-y}{x\left(x+y\right)}\right):\left(\dfrac{y^2}{x\left(x-y\right)\left(x+y\right)}+\dfrac{1}{x+y}\right)\cdot\dfrac{y}{x}\)

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

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

\(=\dfrac{x-y}{y}\cdot\dfrac{y}{x}\)

\(=\dfrac{x-y}{x}\)