Question

Show the Solution of:

dy/dx = -((1+y^2)/(1+x^2)) y(0) = -1
is the inverse tan (x) + inverse tangent (y) = -pi/4

AND show that the above can be written :
y= ((x+1)/(x-1))

And are the graphs of: inverse tan(x) + inverse tan (y) = -pi/4 AND y=((x+1)/(x-1)) from above the same? Explain.