Q.

If the line 2x+6y=2 touches the hyperbola x2-2y2=4, then the point of contact is       [2004]

1 (-2,6)  
2 (-5,26)  
3 (12,16)  
4 (4,-6)  

Ans.

(4)

Equation of tangent to hyperbola x2-2y2=4 at any point (x1,y1) is

xx1-2yy1=4                      ....(i)

But the given tangent is 2x+6y=2

On comparing equation (i) with 2x+6y=2

i.e., 4x+26y=4, we get

x1=4  and  -2y1=26(4,-6) is the required point of contact.