Which two components are necessary to describe an enlargement?

To describe an enlargement accurately, the two key components necessary are the scale factor and the centre of enlargement.

The scale factor indicates how much larger or smaller the new shape will be compared to the original shape. It is crucial because it tells you the ratio of the lengths of corresponding sides in the enlarged shape to the original shape. For instance, a scale factor of 2 means that every dimension of the shape will be doubled.

The centre of enlargement is the point from which the enlargement occurs. It serves as the reference point for all the points in the original shape as they move outward (or inward) to form the enlarged shape. Knowing the centre of enlargement allows you to determine how to position the new shape in relation to the original one accurately.

Together, the scale factor and the centre of enlargement provide a complete description of how a figure has been transformed through enlargement, which is essential in topics related to geometry involving transformations. The other options, while they involve measurements or characteristics of shapes, do not relate specifically to the concept of enlargement.