need the sign conventions for mirrors and lenses

Pls. post each query seperately.

Sign conventions used in mirrors:-

1) All the distances are measured from pole of the mirror.

2) Distances measured in the direction of incident ray are taken as positive.

3) Distances measured in the direction opposite to that of  incident ray are taken as negative.

4) In case of real image (distance of image) is taken as negative and in case of a virtual image , it is taken as positive.

5) The focal length of a convex mirror is taken as positive and that of a concave mirror is taken as negative.