So far I am not really used to see isomorphisms between quotients of formal power series rings.
So let $k$ be an algebraically closed field and let $R:=k[[x,y]]$ be the ring of formal power series in two variables. Furthermore let $f_+:=y^{(n+1)/2}+ix$ and $f_-:=y^{(n+1)/2}-ix$ where $i:=\sqrt{1}$.
How can I see isomorphisms like this one (which I know must be true): $$ k[[x,y]]/(f_+,f_-)\simeq k[[y]]/(y^{(n+1)/2)}) $$