The locus of a point represented by x=a2t+1t, y=a2t−1t, is
an ellipse
a circle
a pair of lines
none of these
We have,
x=a2t+1t,y=a2t−1t⇒ 2xa=1+1t,2ya=1−1t
⇒ 2xa−1=1t,1−2ya=1t
⇒ 2xa−1=1−2ya⇒x+y=ar which is a straight me.