Answer:
[tex]\sqrt{a^2+b^2+16}\text{ units}[/tex]
Step-by-step explanation:
The distance is found using the distance formula:
[tex]d=\sqrt{(x_2-x_1)^2+(y_2-y_1)^2+(z_2-z_1)^2}[/tex]
Then the distance from the given point to the origin is ...
[tex]d=\sqrt{(a-0)^2+(-b-0)^2+(-4-0)^2}\\\\=\boxed{\sqrt{a^2+b^2+16}\ \dots\text{ units}}[/tex]
