Describe regular expression I am learning about regular expression, and  trying to describe a regular expression for the language L

$\qquad L = \{a^i b^j c^k \mid i+j = k\}$

What is the right approach and how to describe a regular expression like this?
It seems I didn't understand the question.
There is no regular expression for this language because it is not regular. You can prove it using the pumping lemma.