The curve described parametrically by x=t2+t+1, and y=t2−t+1 represents
a pair of straight lines
an ellipse
a parabola
a hyperbola
x+y2=t2+1,x−y2=t
Eliminating t , we get
2(x+y)=(x−y)2+4
Since the second-degree terms form a perfect square, itrepresents a parabola ( also ,Δ≠0)