Q.

If 2x-y+1=0 is a tangent to the hyperbola x2a2-y216=1, then which of the following cannot be sides of a right angled triangle            [2017]

1 a,4,1  
2 a,4,2  
3 2a,8,1  
4 2a,4,1  

Ans.

(1, 2, 3)

Given 2x-y+1=0  i.e.  y=2x+1 is a tangent to hyperbola x2a2-y216=1

  c2=a2m2-b2

12=a2×22-16

a2=174a=172

  a,4,1; a,4,2; 2a,8,1  i.e.  172,4,1;   172,4,2;   17,8,1 cannot be the sides of a right triangle.