So basically I have the expression on the form:
(4 ϵ^3 a b )/((-1+ϵ)^2 (a-b)^2)
or $ \frac{4 \epsilon^3 ab }{(\epsilon -1)^2 (a-b)^2} $.
I guess this is a math and Mathematica question. I only want to keep orders of $\epsilon^1$. But I don't know how to collect the $O(\epsilon^2)$ terms when I have something like $(\epsilon -1)^2 $ in the denominator.
Any ideas?
(4 \[Epsilon]^3 a b) Normal@ Series[1/((-1 + \[Epsilon])^2 (a - b)^2), {\[Epsilon], 0, 1}]– Michael E2 Mar 25 '21 at 16:48