You can put this solution on YOUR website!
Note the slope is -2 (down 2, over 1), and the y-intercept is 3. That is how you would graph it manually.
Now, what values can x take on? All.
And, what values can y take on? All.
Thus, D=(-infinity,infinity)
R: R=(-infinity,infinity)
(use the infinity symbol where the words appear above)
or in other symbols,
All real numbers (double-strike R).