If the line ax + by + c = 0 is a tangent to the curve xy = 4, then

For different values of $$\alpha$$, the locus of the point of intersection of the two straight lines $$\sqrt 3 x - y - 4\sqrt 3 \alpha = 0$$ and $$\sqrt 3 \alpha x + \alpha y - 4\sqrt 3 = 0$$ is

The eccentricity of the hyperbola $$4{x^2} - 9{y^2} = 36$$ is

In a plane $$\vec{a}$$ and $$\vec{b}$$ are the position vectors of two points A and B respectively. A point $P$ with position vector $$\overrightarrow{\mathrm{r}}$$ moves on that plane in such a way that $$|\overrightarrow{\vec{r}}-\vec{a}| \sim|\vec{r}-\vec{b}|=c$$ (real constant). The locus of P is a conic section whose eccentricity is