Answer:
[tex]{4}^{45}[/tex]
Step-by-step explanation:
[tex] \huge \: ( {4}^{ \sqrt{81} } )^{5} \\ \\ \huge= ( {4}^{ \sqrt{ {(9)}^{2} } } )^{5} \\ \\\huge= ( {4}^{9 } )^{5} \\ \\\huge= {4}^{9 \times 5} \\ \\\huge= \red{ \boxed{{4}^{45}}} \\ \\[/tex]