I'm trying to solve this problem, but I am having trouble. Can someone give me some pointers?

A curve is defined by the parametric equations:

x = 2t / (1 + t^2)

y = (1 - t^2) / (1 + t^2)

By considering the expression x^2 + y^2, eliminate the parametertto obtain the Cartesian (x-y) equation of the curve.

Thanks