I've asked this question here
Let $A$ be a Banach algebra with identity $e_A$, I'd like to find
$\operatorname{Rad}(A/\operatorname{Rad}(A)).$
whre we define
$\operatorname{Rad}(A)=\{a\in A:e_A-ba \in \text{InvA},b\in A\}$
I think it's equal $\operatorname{Rad}(A)$
but I didn't get any hint how to prove that, please let me know how to prove that
Any piece of advice would be much appreciated.