Pasagot po sana, with solution
13. through (-1,3), m=-3
15. through (2, -3), m= 1/2
17. through (-4, -2), m= -1/3
19. through (5, 0) m= 4/3
21. through (-2, 0) and (2, -4)
23. through (-4, 6) and (4, 0)
25. through (3, -1) and (2, -2)
27. through (1, 2)and (3, -1)
29. through (-2, 4) and (0,-3)
31. a= 3 b= 5
33. a= 4 b= -3
35. a= 2/3 b=4
37. a= 1/5 b= -2/5
39. a= 0 b= -5/7