Put X=t^2+t+1
y=t^2-t+1
Solve this equations to eliminate the t.
x+y=2(t^2+1)
Let x-y=2t
x+y=(1/2)(x-y)^2+2
On rearranging
X^2-2xy+y^2-2x-2y+4=0
Then compare with the general equation of second degree equation i.e. ax2+by2+2hxy+2gx+2fy+c=0. Then you will find that Since, abc+2fgh-af2-bg2-ch2 is not equal to zero and h2=ab. Therefore this equation will represent a parabola