Answer:
![D'(-14,1);\ E'(4,7);\ F'(4,1)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/w21yax31wvap46z269pyd1hc4y3xnlazxg.png)
Explanation:
Since the center of dilation is not at the origin, we can use the following formula in order to find the coordinates of the vertices of the triangle D'E'F':
![D_(O,k)(x,y)=(k(x-a)+a, k(y-b)+b)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/8v5lejqwcv59s9y1crbl10ksci96wnv38v.png)
Where "O" is the center of dilation at (a,b) and "k" is the scale factor.
In this case you can identify that:
![(a,b)=(1,1)\\k=3](https://img.qammunity.org/2020/formulas/mathematics/middle-school/mriako5bbsw0rubc0t5h0tn1u96skvjw5o.png)
Therefore, susbtituting values into the formula shown above, you get that the coordinates ot the resulting triangle D'E'F, are the following:
Vertex D' →
![(3(-4-1)+1,\ 3(1-1)+1)=(-14,1)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/y7bro9x0sfh5zhhm34vnl7kpwlh7w19i8w.png)
Vertex E' →
![(3(2-1)+1,\ 3(3-1)+1)=(4,7)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/2djd8i8engp2jyvzco9a8y0lrfwd2ga32g.png)
Vertex F' →
![(3(2-1)+1,\ 3(1-1)+1)=(4,1)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/u49v75hoywgoawov79msoq5006yl72kn9a.png)