Solution:
Given:
[tex]\sqrt{x-4}\cdot\sqrt{x+1}[/tex]
The expression is defined when the number under the radical sign is not negative. The number under the radical must be greater than or equal to 0.
Hence,
[tex]\begin{gathered} x-4\ge0 \\ x\ge0+4 \\ x\ge4 \\ \\ \\ x+1\ge0 \\ x\ge0-1 \\ x\ge-1 \end{gathered}[/tex]
The inequality that satisfies both cases, therefore, is;
[tex]x\ge4[/tex]
Therefore, OPTION C is correct.
