Question

For exercises 7-10, use the rectangle at the right

Find the coordinates of the image after a dilation by a scale factor of 3.

Short answer

Coordinates of the image after a dilation by a scale factor of 3 are $A\text{'}\left(0,12\right),B\text{'}\left(15,12\right),C\text{'}\left(15,0\right),\text{and}D\text{'}\left(0,0\right)$

Step-by-step solution

- Write Coordinates of rectangle 

From given image, coordinates of the vertices of rectangle are $A\left(0,4\right),B\left(5,4\right),C\left(5,0\right),\text{and}D\left(0,0\right)$

- Vertex matrix after dilation

Vertex matrix of given rectangle is $\left[\begin{array}{cccc}0& 5& 5& 0\\ 4& 4& 0& 0\end{array}\right]$

So vertex matrix of new rectangle after dilation is product of scale factor with vertex matrix of given rectangle as shown below

$3\times \left[\begin{array}{cccc}0& 5& 5& 0\\ 4& 4& 0& 0\end{array}\right]=\left[\begin{array}{cccc}0& 15& 15& 0\\ 12& 12& 0& 0\end{array}\right]$

- Coordinates of image after dilation

As, each coordinate is represented by a column of vertex matrix, so each column represents one coordinate.

Thus, coordinates of image after dilation are

$A\text{'}\left(0,12\right),B\text{'}\left(15,12\right),C\text{'}\left(15,0\right),\text{and}D\text{'}\left(0,0\right)$