Question

y = x/(x+1) <=> x = -y/(y-1)
How can I explain that?

Answer 1

solve
\[y=\frac{x}{x+1}\] for x via
\[y(x+1)=x\]
\[yx+y=x\]
\[yx-x=-y\]
\[(y-1)x=-y\]
\[x=\frac{-y}{y-1}\]

Answer 2

Thanks!