In Problems 9-26, find a particular solution to the differential equation. 9. y" + 3y = 9 11. y"(x) + y(x) = 2* 13. y" - y' +9y = 3 sin 3t 15. d'y dx dy -5+6y= xet dx 17. y" + 4y 8 sin 2t 19. 4y" + 11y' - 3y = -2te-t 20. y" + 4y = 16t sin 2t 21. x" (1) - 4x' (1) + 4x(1) 10. y" + 2y' - y = 10 12. 2x' + x = 31 14. 2z" +z = 9et 16. 0"(t)-0(t) = t sint 18. y" - 2y + y = 8e te1 In Problems 27-32, determine the form of a particular solution for the differential equation. (Do not evaluate coefficients.) 27. y" +9y = 4t sin3t 28. y"-6y' +9y = 5tet 29. y" + 3y'- 7y = te 30. y"-2y + y = 7e' cost 31. y" + 2y' + 2y = 81e sin t 32. y"-y'- 12y = 21e 3