Các khẳng định sau đúng hay sai?
\(\left(\dfrac{x}{y}\right)^n.\left(\dfrac{x}{y}\right)^m=\left(\dfrac{x}{y}.\dfrac{x}{y}\right)^{n+m}\) với \(y \neq 0\).\(\left(\dfrac{x}{y}\right)^n.\left(\dfrac{x}{y}\right)^m=\left(\dfrac{x}{y}\right)^{n+m}\) với \(y \neq 0\).\(\left(\dfrac{x}{y}\right)^n.\left(\dfrac{x}{y}\right)^m=\left(\dfrac{x}{y}\right)^{n-m}\) với \(y \neq 0\).\(\left(\dfrac{x}{y}\right)^n:\left(\dfrac{x}{y}\right)^m=\left(\dfrac{x}{y}\right)^{m-n}\) với \(y \neq 0\).