We have 2 expressions:
[tex]\begin{gathered} a)\text{ }\sqrt[]{-4} \\ b)\sqrt[]{-5} \end{gathered}[/tex]Case a.
We can rewrite our square root as
[tex]\sqrt[]{-4}=\sqrt[]{-1\times4}=\sqrt[]{-1}\times\sqrt[]{4}[/tex]but by definition
[tex]\sqrt[]{-1}=i[/tex]which is the imaginary number. So, our square root is equal to
[tex]\sqrt[]{-4}=\sqrt[]{4}i[/tex]which corresponds to option 3.
Case b.
Similarly,
[tex]\sqrt[]{-5}=\sqrt[]{-1}\times\sqrt[]{5}[/tex]and the answer is
[tex]\sqrt[]{-5}=i\sqrt[]{5}[/tex]which corresponds to option 6