Question
If the line $$2x + \sqrt 6 y = 2$$ touches the hyperbola $${x^2} - 2{y^2} = 4,$$ then the point of contact is-
A.
$$\left( { - 2,\,\sqrt 6 } \right)$$
B.
$$\left( { - 5,\,2\sqrt 6 } \right)$$
C.
$$\left( {\frac{1}{2},\,\frac{1}{{\sqrt 6 }}} \right)$$
D.
$$\left( {4,\, - \sqrt 6 } \right)$$
Answer :
$$\left( {4,\, - \sqrt 6 } \right)$$
Solution :
Equation of tangent to hyperbola $${x^2} - 2{y^2} = 4$$ at any point $$\left( {{x_1},\,{y_1}} \right)$$ is $$x{x_1} - 2y{y_1} = 4$$
Comparing with $$2x + \sqrt 6 y = 2$$ or $$4x + 2\sqrt 6 y = 4$$
$$ \Rightarrow {x_1} = 4$$ and $$ - 2{y_1} = 2\sqrt 6 \Rightarrow \left( {4,\, - \sqrt 6 } \right)$$ is the required point.