Since, point of intersection is on both the curves, then y12=6x1 ......(i) and 9x12+by12=16 .....(ii) Now, find the slope of tangent to both the curves at the point of intersection P(x1,y1) For slope of curves: Curve (i): (
dy
dx
)(x1,y1)=m1=
3
y1
Curve (ii): and (
dy
dx
)(x1,y1)=m2=−
9x1
by1
Since, both the curves intersect each other at right angle then, m1m2=−1⇒