А, б

№150

а) \(\left(\frac{x}{y^2}-\frac{1}{x}\right):\left(\frac{1}{y}+\frac{1}{x}\right)=\frac{x^2-y^2}{xy^2}\cdot\frac{xy}{x+y}=\frac{x-y}{y}\).

б) \(\left(\frac{a}{m^2}+\frac{a^2}{m^3}\right):\left(\frac{m^2}{a^2}+\frac{m}{a}\right)=\frac{a(m+a)}{m^3}\cdot\frac{a^2}{m(m+a)}=\frac{a^3}{m^4}\).

Ответ: а) \(\frac{x-y}{y}\); б) \(\frac{a^3}{m^4}\).