Answer: The nature of the image formed by a concave mirror can be determined based on the sign of the magnification produced.
(a) If the magnification is positive (+3), it indicates that the image is magnified and upright. In this case, the image is virtual and located on the same side as the object. The size of the image will be three times larger than the size of the object.
(b) If the magnification is negative (-1), it indicates that the image is diminished and inverted. In this case, the image is real and located on the opposite side of the object. The size of the image will be the same as the size of the object, but it will be inverted.
It's important to note that the actual size of the image cannot be determined solely based on the magnification. The magnification only gives information about the relative size of the image compared to the object. To determine the actual size, additional information, such as the size and distance of the object, is required.