Stack Exchange network consists of 183 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.
@AliTaghavi Because $\mathbb{H}$ is not commutative, you can't always collect all the terms of the form $a_0q a_1 q a_2\cdots a_{n-1}q a_n$ (with $a\in \mathbb{H}$) into a single term of the form $a q^n$.
