Answer:
![(f + g)(x) = - 10 \sqrt[3]{2x} \: \: \: (f + g)( - 4) = 20](https://tex.z-dn.net/?f=%28f%20%2B%20g%29%28x%29%20%20%3D%20%20-%2010%20%5Csqrt%5B3%5D%7B2x%7D%20%20%5C%3A%20%20%5C%3A%20%20%5C%3A%20%28f%20%2B%20g%29%28%20-%204%29%20%3D%2020)
![(f - g)(x) =12 \sqrt[3]{2x} \: \: \: (f - g)( - 4) = - 24](https://tex.z-dn.net/?f=%28f%20%20-%20%20g%29%28x%29%20%20%3D12%20%5Csqrt%5B3%5D%7B2x%7D%20%20%5C%3A%20%20%5C%3A%20%20%5C%3A%20%28f%20%20-%20g%29%28%20-%204%29%20%3D%20%20%20-%2024)
The domain of (f+g)(x) is all real numbers.
The domain of (f-g)(x) is all real numbers.
Step-by-step explanation:
The given functions are
![f(x) = \sqrt[3]{2x}](https://tex.z-dn.net/?f=f%28x%29%20%3D%20%20%5Csqrt%5B3%5D%7B2x%7D%20)
and
![g(x) =- 11\sqrt[3]{2x}](https://tex.z-dn.net/?f=g%28x%29%20%3D-%2011%5Csqrt%5B3%5D%7B2x%7D%20)
By the algebraic properties of polynomial functions:

![(f + g)(x) = \sqrt[3]{2x} + - 11 \sqrt[3]{2x}](https://tex.z-dn.net/?f=%28f%20%2B%20g%29%28x%29%20%3D%20%20%5Csqrt%5B3%5D%7B2x%7D%20%20%2B%20%20-%2011%20%5Csqrt%5B3%5D%7B2x%7D%20)
This becomes:
![(f + g)(x) = \sqrt[3]{2x} - 11 \sqrt[3]{2x}](https://tex.z-dn.net/?f=%28f%20%2B%20g%29%28x%29%20%3D%20%20%5Csqrt%5B3%5D%7B2x%7D%20%20-%2011%20%5Csqrt%5B3%5D%7B2x%7D)
We subtract to obtain:
![(f + g)(x) = - 10 \sqrt[3]{2x}](https://tex.z-dn.net/?f=%28f%20%2B%20g%29%28x%29%20%20%3D%20%20-%2010%20%5Csqrt%5B3%5D%7B2x%7D%20)
Also

![(f - g)(x) = \sqrt[3]{2x} - - 11 \sqrt[3]{2x}](https://tex.z-dn.net/?f=%28f%20%20-%20g%29%28x%29%20%3D%20%20%5Csqrt%5B3%5D%7B2x%7D%20%20-%20-%20%2011%20%5Csqrt%5B3%5D%7B2x%7D%20)
![(f - g)(x) = \sqrt[3]{2x} + 11 \sqrt[3]{2x}](https://tex.z-dn.net/?f=%28f%20%20-%20g%29%28x%29%20%3D%20%20%5Csqrt%5B3%5D%7B2x%7D%20%2B%20%2011%20%5Csqrt%5B3%5D%7B2x%7D%20)
![(f - g)(x) = 12\sqrt[3]{2x}](https://tex.z-dn.net/?f=%28f%20%20-%20g%29%28x%29%20%3D%20%2012%5Csqrt%5B3%5D%7B2x%7D)
When x=-4
![(f + g)( - 4) = - 10\sqrt[3]{2 \times - 4}](https://tex.z-dn.net/?f=%28f%20%20%20%2B%20g%29%28%20-%204%29%20%3D%20-%2010%5Csqrt%5B3%5D%7B2%20%5Ctimes%20%20-%204%7D%20)
![(f + g)( - 4) = - 10\sqrt[3]{ - 8}](https://tex.z-dn.net/?f=%28f%20%20%20%2B%20g%29%28%20-%204%29%20%3D%20-%2010%5Csqrt%5B3%5D%7B%20-%208%7D%20)

Then also;
![(f - g)( - 4) = 12\sqrt[3]{ - 8}](https://tex.z-dn.net/?f=%28f%20%20-%20%20g%29%28%20-%204%29%20%3D%2012%5Csqrt%5B3%5D%7B%20-%208%7D%20)

The domain refers to the values that makes the function defined.
Both are cube root functions and are defined for all real numbers.
The domain of (f+g)(x) is all real numbers.
The domain of (f-g)(x) is all real numbers.