AP EAMCET2007MathematicsHyperbola
If the line l x+m y=1 is a normal to the hyperbola x^2 a^2 - y^2 b^2 =1 , then a^2 l^2 - b^2 m^2 is equal to
Options
- Aa^2-b^2
- Ba^2+b^2
- C(a^2+b^2 )^2
- D(a^2-b^2 )^2
Correct answer
C. (a^2+b^2 )^2
Step-by-step solution
If l x+m y+n=0 is normal to the hyperbola x^2 a^2 - y^2 b^2 =1 Then a^2 l^2 - b^2 m^2 = (a^2+b^2 )^2 n^2 Here, n=-1 , therefore a^2 l^2 - b^2 m^2 = (a^2+b^2 )^2 .