[tex]Answer:\ \boxed{5^2}[/tex]
[tex]\sqrt[n]{a}=a^\frac{1}{n}\\\\\text{therefore}\\\\\sqrt5=5^\frac{1}{2}\\----------------\\25=5^2\\----------------\\78,125=5^7\\----------------\\\text{use}\\\\a^n\cdot a^m=a^{n+m}\\\\\dfrac{a^n}{a^m}=a^{n-m}\\----------------\\\\\dfrac{\sqrt5\times78,125}{25\times5^{\frac{7}{2}}}=\dfrac{5^\frac{1}{2}\times5^7}{5^2\times5^\frac{7}{2}}=\dfrac{5^{\frac{1}{2}+7}}{5^{2+3\frac{1}{2}}}=\dfrac{5^{7\frac{1}{2}}}{5^{5\frac{1}{2}}}=5^{7\frac{1}{2}-5\frac{1}{2}}=\boxed{5^2}[/tex]
