Question

To find the value of v for different values of u in case of concave mirror solutions

Answer 1

The value of u is always been considered as negative, as the object is always kept in front of concave mirror or in the left direction of the plane.
The magnitude of v is considered positive when the image formed behind the concave mirror, that is when the image formed is virtual image.
The focal length of the mirror can be calculated by using the relation ;
1/f = (1/v)+(1/u)

hope it helps you...