Scale factor 1/2 means all the points be 1/2 of original.
Point A is (0,4)
Point B is (4,2)
So,
Point A' would be (0,2)
Point B' would be (2,1)
The distance between them would be followed by distance formula:
![D=\sqrt[]{(y_2-y_1)^2+(x_2-x_1)^2}](https://img.qammunity.org/2023/formulas/mathematics/college/bn18956xdzpj56va064oiuu2531qoyd8xa.png)
Keeping the points of A' and B' and putting into formula, we have:
![\begin{gathered} D=\sqrt[]{(y_2-y_1)^2+(x_2-x_1)^2} \\ D=\sqrt[]{(1-2)^2+(2-0)^2} \\ D=\sqrt[]{(-1)^2+(2)^2} \\ D=\sqrt[]{1+4} \\ D=\sqrt[]{5} \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/9ayxsjn05htbehamzijgfowmhno6ib4ln2.png)
So,
3rd andswer choice is rright
![D=\sqrt[]{5}](https://img.qammunity.org/2023/formulas/mathematics/college/hhimqjrx4hg93l5ce7y11uiizbxc3vkvil.png)