Show that if $(z+1)^100 = (z-1)^100$, then $z$ is purely imaginary
Clash Royale CLAN TAG #URR8PPP up vote 7 down vote favorite Let $z$ be a complex number satisfying $$(z+1)^100 = (z-1)^100$$ Show that $z$ is purely imaginary, i.e. that $Re(z) = 0$. Rearrange to $$left(fracz+1z-1right)^100 = 1$$ I tried using $z = x+iy$ and trying to multiply numerator and denominator by the conjugate, but I hit a roadblock. I also tried substituting $1 = -e^ipi$, but that also doesn't seem to get me anywhere. How can I prove this? Any help is appreciated, thank you! complex-analysis complex-numbers share | cite | improve this question edited 3 mins ago TheSimpliFire 11k 6 21 54 asked 7 hours ago Chinmayee Gidwani 46 2 New contributor Chinmayee Gidwani is a new contributor to this site. Take care in asking for clarification, commenting, and answering. Check out our Code of Conduct. add a comment  | up vote 7 down vote favorite Let $z$ be a complex number sa...