How to show(Prove) the composition of two polynomials is a polynomial,
the composition of two rational function is a rational function?
We just start learning complex analysis, and there is a formula of complex polynomial function we are given in lecture.
p(z) = $c\prod^{d}_{i=1}(z-a_i)^{m_i}$
where $a_j$ are all distinct, and $m_i$ add to degree p.
Thank you for helps, first time ask a question on MathStack.