Because k 1k4≠0

So k 1≠0 k4≠0

So α 1 can be expressed linearly by α2, α3 and α4.

Then α 1, α2 and α3 can be expressed linearly by α2, α3 and α4.

Conversely, α2, α3 and α4 can also be expressed linearly by α 1, α2 and α3.