Which of the following ore does NOT show the correct formula?

The quadratic equation whose roots are I and  where 

In zone-refining method the molten zone

Four newly  married couples are dancing at a function the selection of the partner is random. The number of ways that exactly one husband  is not dancing with his own wife is

There are 12 intermediate stations on a railway line between 2 stations. The number  number of ways that a train can be made to stop at 4 of these intermediate stations no two of these halting stations being consecutive is

The number of ways of forming an arrangement of 4 letters from the letters of the word "IITJEE" is

 equal to

is equal to

If then

For such questions, we should know how to find the dot product and cross product. Dot product of two vectors is always a scalar quantity. The cross product of two vectors is a vector quantity.

If are non coplanar vectors then the roots of equation

The point of intersection of the plane will the stright line passing through the origin and perpendicular to the plane is

The position vector of the centre of the circle

The locus of midpoints of chords of  which subtend a right angle  at the centre is