Răspuns:
[tex]\displaystyle{ [(\frac{5}{7})^{8}]^{10} : (\frac{5}{7})^{78} = }[/tex]
[tex]\displaystyle{ = (\frac{5}{7})^{8 \cdot 10} : (\frac{5}{7})^{78} }[/tex]
[tex]\displaystyle{ = (\frac{5}{7})^{80} : (\frac{5}{7})^{78} }[/tex]
[tex]\displaystyle{ = (\frac{5}{7})^{80-78} }[/tex]
[tex]\displaystyle{ = (\frac{5}{7})^{2} }[/tex]
[tex]\displaystyle{ = \frac{5^{2} }{ 7^{2} } }[/tex]
[tex]\displaystyle{ = \frac{25}{49} }[/tex]
