If the curves y² = 6x, 9x² + by² = 16 intersect each other at right angles, then the value of b is :

If $$\beta $$ is one of the angles between the normals to the ellipse, x² + 3y² = 9 at the points (3 cos $$\theta $$, $$\sqrt 3 \sin \theta $$) and ($$-$$ 3 sin $$\theta $$, $$\sqrt 3 \,\cos \theta $$); $$\theta \in \left( {0,{\pi \over 2}} \right);$$ then $${{2\,\cot \beta } \over {\sin 2\theta }}$$ is equal to :

If a right circular cone, having maximum volume, is inscribed in a sphere of radius 3 cm, then the curved surface area (in cm²) of this cone is :

The function f defined by

f(x) = x³ $$-$$ 3x² + 5x + 7 , is :