a.\(\left(x-\dfrac{x^2+x^2}{x+y}\right).\left(\dfrac{1}{y}+\dfrac{2}{x-y}\right)\)

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

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

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

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

b.\(\dfrac{2}{xy}:\left(\dfrac{1}{x}-\dfrac{1}{y}\right)-\dfrac{x+y}{\left(x-y\right)^2}\)

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

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

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

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

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

Cho mik hỏi hỗn hợp khí X gồm NO và gì nữa ạ?

\(4Na+O_2\rightarrow\left(t^o\right)2Na_2O\)

\(Na_2O+H_2O\rightarrow2NaOH\)

\(NaOH+2HCl\rightarrow NaCl+H_2O\)

\(NaCl+AgNO_3\rightarrow AgCl\downarrow+NaNO_3\)