### 813 Recommended Exercises

Abbreviations and special notation used in denoting certain exercises:
!
especially important to do thoroughly and carefully
?
not clear if worth doing
NB
note well the result obtained; no comment on worth doing
+NB
note well the result obtained and worth doing
--
linked: regard as parts of one exercise (NOTE: 5--7 means 5 and 7 are linked, and says nothing about 6.)
[Chapter.section, pages #exercises.]
• XV.1, 500--1 #1, 3, 4, 5, 6, and 10.Determine the monics and epics in the category of positive integers with arrows "divides."
• XV.2, 504 #5, 6, 11.
• XV.3, 506 #2.
• XV.4, 511 #All except possibly #8.(c).
• XV.5, 516 #All except possibly #9.
• XV.6, 520 #1, 3, 4, 5, NB7--8, 10--11, NB12, 13, ?14.

• XVI.1, 524 #3 {first part only}, 4, 5, 6, 7, 8.
• XVI.2, 530 #3, 6, 7, 8, 9.
• XVI.3, 533 #1, 2, 3, NB4, !6, 7--8--9.
• XVI.4, 538--9 #2, NB3, 4--5, 7--8, 9, NB10, 11, ?12--13.
• XVI.5, 542--3 #1--2, 4--5--6, 7.
• XVI.6, 547 #2, ?3, 4.
• XVI.7, 551--2 #3, 4.
• XVI.8, 555 #1, NB2, 3.(a).
• XVI.9, 558 #1.
• XVI.10, 560 #1, 2--3, 4.

• XIII.1, 439 #1, 2, NB3.
• XIII.2, 442 #1, 3, 4, 5, 6, NB7.
• XIII.3, 444--5 #?1, 2, 3, 4, ?5, ?6, 7, 8, !9, ?10.(a), 10.(b).
• XIII.4, 446 #1, 2.
• XIII.5, 450 #1, 2, 3, NB4: product of fields.
• XIII.6, 453 #?1, 2, 3--4--5, 6, NB 7 through 11.
• XIII.7, 456 #1, 2, 3, 4.
• XIII.8, 458 #1, 2, 3, 4, 5.
• XIII.9, 461 #1, ?2, ?3.
• XIII.10, 464--5 #!1, 2, 3, 4, 5, 6, 7, 8, 9, 10.
• XIII.11, 469 #1, 2, +NB3, 4, "5:" converse of Thm. 17 !