Given:
The coordinates of point A are (7,4).
It is dilated from the origin by a scale factor r = 3.
To find:
The coordinates of A'.
Solution:
If a figure is dilated from the origin by a scale factor k, then
![(x,y)\to (kx,ky)](https://img.qammunity.org/2022/formulas/mathematics/high-school/e3lacytewqtltsvoqbo5laayjcqqy00l4a.png)
Here, the figure is dilated from the origin by a scale factor 3, so the rule of dilation is given by:
![(x,y)\to (3x,3y)](https://img.qammunity.org/2022/formulas/mathematics/high-school/qwxpfkmjgbrwxsthvlsku3d31h5rnt6in8.png)
Using this rule, we get
![A(7,4)\to A'(3(7),3(4))](https://img.qammunity.org/2022/formulas/mathematics/high-school/rikoshy0dd8yxccgao3o16c0ps9uqdlisv.png)
![A(7,4)\to A'(21,12)](https://img.qammunity.org/2022/formulas/mathematics/high-school/41ukqdrt77npjncqt24i1fwa9gedmy2zga.png)
Therefore, the coordinates of point A' are (21,12).