Các khẳng định sau đúng hay sai?
\(\left(\dfrac{1}{5}\right)^n.\left(\dfrac{25}{4}\right)^m=\dfrac{5^{n+m}}{4^{n+m}}.\)\(\left(\dfrac{1}{5}\right)^n.\left(\dfrac{25}{4}\right)^m=\dfrac{5}{4^{n+m}}.\)\(\left(\dfrac{1}{5}\right)^n.\left(\dfrac{25}{4}\right)^m=\left(\dfrac{5}{4}\right)^n\)\(\left(\dfrac{1}{5}\right)^n.\left(\dfrac{25}{4}\right)^m=\left(\dfrac{5}{4}\right)^{n+m}.\)