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Negative enlargements from a centre of enlargement on a coordinate grid.

Updated on April 19, 2011

In order to enlarge a shape by a negative scale factor from a centre of an enlargement:

Step 1: Count the distances from the centre of the enlargement to each corner of your shape.

Step 2: Multiply these distances by your scale factor and change your directions. So for example, if the scale factor is -2 and the distance from the centre of enlargement to a corner is 3 up and 5 right, then your new directions will be 6 down and 10 left.

Step 3: Count out the new direction from the centre of your enlargement and join up the corners to create you enlarged shape.

Example

Enlarge this shape by a scale factor -3 from the point (1,0)

Step 1: Count the distances from the centre of the enlargement to each corner of your shape.

Corner 1 = 2 right and 3 up

Corner 2 = 3 right 3 down

Corner 3 = 2 left

Step 2: Multiply these distances by your scale factor and change your directions.

New Corner 1 = 6 left 9 down

New Corner 2 = 9 left 9 up

New Corner 3 = 6 right

Step 3: Count out the new direction from the centre of your enlargement and join up the corners to create you enlarged shape.

Make sure that the directions have been counted from the centre of the enlargement.

If you are finding this example difficult then you might not have understood enlarging shapes from a centre of enlargement using a positive scale factor. Also, make sure that you always count the directions from the centre to the corner and not from the corner to the centre.

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