What is the nature of the image formed by a concave mirror if the magnification produced by the mirror is +3?

The image formed by a concave mirror with a magnification of +3, will be virtual and erect, because the positive sign $(+)$ of magnification indicates that the height of both the object and the image is above the principal axis.

Explanation

Since the value of magnification produced by the concave mirror has a positive $(+)$ value, which represents that the image formed will be virtual, erect and enlarged. It also represents that, the height of both the object and the image is above the principal axis.