1. optimization

3. constraints, feasible

5. True

7. True

9. Max 18, Min 5

11. Max 26, Min 7

13. Max 66, Min 13

15. Maximum value is (2, 3) (4, 5) (6, 1) ${\displaystyle \frac{1284}{19}}\text{ at }\left({\displaystyle \frac{56}{19}},{\displaystyle \frac{60}{19}}\right).$

17. Maximum value is 410 at (40, 30)

19. Minimum value is 3 at (3, 0)

21. Minimum value is 1364 at (8, 84)

23. Maximum value is 54 at (3.6, 0)

25. Minimum value is 400 for all (x, y) on the line segment between (20, 15) and (50, 0).