Answer:
[tex]\large\boxed{\sqrt{49a^8}=7a^4}[/tex]
Step-by-step explanation:
[tex]\sqrt{49a^8}\\\\\text{use}\ \sqrt{ab}=\sqrt{a}\cdot\sqrt{b}\\\\=\sqrt{49}\cdot\sqrt{a^8}=7\sqrt{a^8}\\\\\text{use}\ (a^n)^m=a^{nm}\\\\=7\sqrt{a^{4\cdot2}}=7\sqrt{(a^4)^2}\\\\\text{use}\ \sqrt{a^2}=a\\\\=7a^4[/tex]