y = (1+x)/(1-x)

How do I rearrange that equation to be:

x = (y-1)/(y+1)

2 answers

multiply both sides by 1-x

y-xy=1+x
subtract one, add xy to each side
y-1=x+xy=x(1+y)
solve for x.
Ah, thanks so much. My mind is working slowly today :)