3.4 Exercises In Exercises 1-10, determine whether the given relation is an equivalence relation on (1, 2, 3, 4, 5). If the relation is an equiv- alence relation, list the equivalence classes. (In Exercises 5-10, x, ye (1, 2, 3, 4, 5).) 1. {(1, 1), (2, 2), (3, 3), (4,4), (5, 5), (1, 3), (3, 1)) 2. {(1, 1), (2, 2), (3, 3), (4,4), (5,5), (1, 3), (3, 1), (3, 4). (4,3)} 3. ((1, 1), (2, 2), (3, 3), (4,4)) 4. {(1, 1), (2, 2), (3, 3), (4,4), (5, 5), (1, 5), (5, 1), (3,5), (5,3), (1,3), (3, 1)) 5. ((x, y) | 1 ≤x≤ 5 and 1 ≤ y ≤5) 6. ((x, y) | 4 divides .x - y) 8. [(x, y) | x divides 2-y) 7. {(x, y) | 3 divides x + y) 9. {(x, y) |x and y are both even} 10. {(x, y) | x and y are both even or x and y are both odd} In Exercises 11-16, determine whether the given relation is an equivalence relation on the set of all people. 11. [(x, y) |x and y are the same height) 12. {(x, y) |x and y have, at some time, lived in the same country} 13. {(x, y) |x and y have the same first name} 14. [(x, y) |x is taller than y) 15. ((x, y) [x and y have the same parents} 16. ((x, y) [x and y have the same color hair} In Exercises 17-22, list the members of the equivalence relation on (1,2,3,4) defined (as in Theorem 3.4.1) by the given partition. Also, find the equivalence classes [1], [2], [3], and [4]. 17. (1.2), (3, 4)) 19. (1). (2). (3). (4}} 21. [1,2,3,4]} 18. (1), (2), (3,4)) 20. ((1,2,3), (4)) 22. (1), (2, 4), (3}} In Exercises 23-25, let X=(1, 2, 3, 4, 5), Y=(3, 4), and C= (1.3). Define the relation R on P(X), the set of all subsets of X, as ARB if AUY=BUY. 23. Show that R is an equivalence relation. 24. List the elements of [C], the equivalence class containing C. 25. How many distinct equivalence classes are there? 26. Let X = (San Francisco, Pittsburgh, Chicago, San Diego, Philadelphia, Los Angeles). Define a relation R on X as x Ry if x and y are in the same state. (a) Show that R is an equivalence relation. (b) List the equivalence classes of X. 27. If an equivalence relation has only one equivalence class, what must the relation look like? 28. If R is an equivalence relation on a finite set X and X = [R]. what must the relation look like? 29. By listing ordered pairs, give an example of an equivalence relation on [1, 2, 3, 4, 5, 6) having exactly four equivalence classes. 30. How many equivalence relations are there on the set (1, 2, 3)? 31. Let R be a reflexive relation on X satisfying: for all x, y, z € X, if x Ry and y Rz, then z R.x. Prove that R is an equivalence re- lation. 32. Define a relation R on RR, the set of functions from R to R. byf Rg if f(0) = g(0). Prove that R is an equivalence relation on RR. Let f(x) = x for all x € R. Describe [f]. 33. Define a relation R on RR, the set of functions from R to R by fRg if there exist a, b R such that f(x) = g(x + a) + b for all x R. Prove that R is an equivalence relation on RR. What property do all functions in an equivalence class share? 34. Let X= [1,2,..., 10). Define a relation R on Xx X by (a, b) R (c,d) if a +d=b+c. (a) Show that R is an equivalence relation on X X X. (b) List one member of each equivalence class of X X X. 35. Let X = (1,2,.... 10). Define a relation R on X X X by (a, b) R (c,d) if ad=bc. (a) Show that R is an equivalence relation on X X X. (b) List one member of each equivalence class of X X X. (c) Describe the relation R in familiar terms. 36. Let R be a reflexive and transitive relation on X. Show that ROR is an equivalence relation on X.
3.4 Exercises In Exercises 1-10, determine whether the given relation is an equivalence relation on (1, 2, 3, 4, 5). If the relation is an equiv- alence relation, list the equivalence classes. (In Exercises 5-10, x, ye (1, 2, 3, 4, 5).) 1. {(1, 1), (2, 2), (3, 3), (4,4), (5, 5), (1, 3), (3, 1)) 2. {(1, 1), (2, 2), (3, 3), (4,4), (5,5), (1, 3), (3, 1), (3, 4). (4,3)} 3. ((1, 1), (2, 2), (3, 3), (4,4)) 4. {(1, 1), (2, 2), (3, 3), (4,4), (5, 5), (1, 5), (5, 1), (3,5), (5,3), (1,3), (3, 1)) 5. ((x, y) | 1 ≤x≤ 5 and 1 ≤ y ≤5) 6. ((x, y) | 4 divides .x - y) 8. [(x, y) | x divides 2-y) 7. {(x, y) | 3 divides x + y) 9. {(x, y) |x and y are both even} 10. {(x, y) | x and y are both even or x and y are both odd} In Exercises 11-16, determine whether the given relation is an equivalence relation on the set of all people. 11. [(x, y) |x and y are the same height) 12. {(x, y) |x and y have, at some time, lived in the same country} 13. {(x, y) |x and y have the same first name} 14. [(x, y) |x is taller than y) 15. ((x, y) [x and y have the same parents} 16. ((x, y) [x and y have the same color hair} In Exercises 17-22, list the members of the equivalence relation on (1,2,3,4) defined (as in Theorem 3.4.1) by the given partition. Also, find the equivalence classes [1], [2], [3], and [4]. 17. (1.2), (3, 4)) 19. (1). (2). (3). (4}} 21. [1,2,3,4]} 18. (1), (2), (3,4)) 20. ((1,2,3), (4)) 22. (1), (2, 4), (3}} In Exercises 23-25, let X=(1, 2, 3, 4, 5), Y=(3, 4), and C= (1.3). Define the relation R on P(X), the set of all subsets of X, as ARB if AUY=BUY. 23. Show that R is an equivalence relation. 24. List the elements of [C], the equivalence class containing C. 25. How many distinct equivalence classes are there? 26. Let X = (San Francisco, Pittsburgh, Chicago, San Diego, Philadelphia, Los Angeles). Define a relation R on X as x Ry if x and y are in the same state. (a) Show that R is an equivalence relation. (b) List the equivalence classes of X. 27. If an equivalence relation has only one equivalence class, what must the relation look like? 28. If R is an equivalence relation on a finite set X and X = [R]. what must the relation look like? 29. By listing ordered pairs, give an example of an equivalence relation on [1, 2, 3, 4, 5, 6) having exactly four equivalence classes. 30. How many equivalence relations are there on the set (1, 2, 3)? 31. Let R be a reflexive relation on X satisfying: for all x, y, z € X, if x Ry and y Rz, then z R.x. Prove that R is an equivalence re- lation. 32. Define a relation R on RR, the set of functions from R to R. byf Rg if f(0) = g(0). Prove that R is an equivalence relation on RR. Let f(x) = x for all x € R. Describe [f]. 33. Define a relation R on RR, the set of functions from R to R by fRg if there exist a, b R such that f(x) = g(x + a) + b for all x R. Prove that R is an equivalence relation on RR. What property do all functions in an equivalence class share? 34. Let X= [1,2,..., 10). Define a relation R on Xx X by (a, b) R (c,d) if a +d=b+c. (a) Show that R is an equivalence relation on X X X. (b) List one member of each equivalence class of X X X. 35. Let X = (1,2,.... 10). Define a relation R on X X X by (a, b) R (c,d) if ad=bc. (a) Show that R is an equivalence relation on X X X. (b) List one member of each equivalence class of X X X. (c) Describe the relation R in familiar terms. 36. Let R be a reflexive and transitive relation on X. Show that ROR is an equivalence relation on X.
Advanced Engineering Mathematics
10th Edition
ISBN:9780470458365
Author:Erwin Kreyszig
Publisher:Erwin Kreyszig
Chapter2: Second-order Linear Odes
Section: Chapter Questions
Problem 1RQ
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