Ch.1.2(16)

[Emman Subhani]

$$u_{t} + u_{xxxx} + u=0 \tag{1.2.16}$$
I understand that the first part of the equation ( $u_t +u_{xxxx}$) is definitely Linear Homogenous. However, the $u$ in the last part is confusing me and I am stuck between two answers - linear homogenous or semi linear?

[Victor Ivrii]

Part $u$ is also linear and homogeneous$. Thus the correct and precise answer is linear homogeneous.