From the book

The chapter on Second-Order Differential Equations, as well as the associated appendix section on complex numbers, has been moved to the website.

It doesn't mention a reason in the book and I couldn't find an answer after searching the internet. Is there a reason related to pedagogy? Does the publisher profit from it?

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    $\begingroup$ Pages cost money, and make the book heavy. If some people want those sections, but most people don't care, putting them online seems sensible to me. $\endgroup$
    – Sue VanHattum
    Jan 8, 2022 at 17:18
  • $\begingroup$ @SueVanHattum do you think, in general, moving content from textbooks into websites is a move in the right direction? $\endgroup$ Jan 8, 2022 at 21:38
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    $\begingroup$ Depends. Calculus books have so much in them, and the schools I've taught at don't do the differential equations chapter, because we teach differential equations in another course. $\endgroup$
    – Sue VanHattum
    Jan 8, 2022 at 22:04

2 Answers 2


Nevertheless, things may not be as they seem. The excised material is available in Stewart's 6th edition Calculus. The material on complex numbers is within the scope of information covered algebra and trigonometry, or in a pre-calculus or math analysis course. The material on second order differential equations is supplemental and suitable for inclusion in a general course on differential equations. The publishing editor's decision to remove this material from the 9th edition text was apparently intended to focus the subject matter more succinctly on Calculus as the principal subject. This is understandable, particularly since further study in the subjects comprising complex numbers and second order differential equations is more advanced and specific to study in those areas


It's probably not just cost control--it's revenue capture. There's definitely some MBA games going on in academic publishing. Just look at the edition frequency (that's not to design a better book, it's to mess with the resale market). So when you see these sort of alternate payment models always suspect a revenue scheme.

  1. Sometimes you have to buy (or have your school buy) membership in a online HW-solver type of club to see these extras. This is extra $$ for the publisher. And also a means of control for colleges (i.e. making it harder for self studiers. Gatekeeper stuff.

  2. Furthermore any online structure is a hassle since it is not resalable. It's also not enduring. What if the provider goes defunct, for example? It's like the trend in "software as a service" rather than having a CD. (Same with movies from streaming services versus buying a CD.)

  3. I'm not sure about your specific example. But I suspect some of the game with the online service (for extras or for HW) is related to edition control. For example, they can STOP having the online Xth edition content when they come out with X+1 or X+2. (see intro.)

  4. More tenuous but still conceivable is something related to "price discrimination". https://en.wikipedia.org/wiki/Price_discrimination Marketers try to come up with schemes to separate the cost sensitive from cost insensitive and then charge different prices (often with trivial differences in the product). The point here is to compete on price only when you need to. (With a total free market, transparency, and a commodity product this is impossible. But there are many deviations from ideality. So marketers try to exploit. This is why discounting exists for instance, versus just across the board price changes like on oil, grain, etc.) I don't know exactly how they'd tie it in with a price discrimination scheme, but it's the sort of thing marketers think about.

Other than that, it's probably slightly related to the AP BC change (slow and small step backwards in coverage, "dumbing down" by cutting content). They cut 2nd order diffyQs a few years ago. (Also shells for volumes of rotation.) I think lots of colleges still have it. And it's sort of a normal part of a traditional text (Granville, old Thomas, etc.) So they probably need to keep it in for schools that haven't dumbed down yet like AP did. But AP is probably a huge market. And may be a trend that some colleges are also following, to water down.

P.s. After writing this I did a quick Google search on 'use of online content to capture revenue in textbook publishing'. Several articles came back, talking about this as a scheme for publishers to fight the used market. For example:


(Note this is a 2013 article--not a new MBA game.)

P.s.s. One of the things that makes it possible for publishers to play these games is the partnership with schools (gatekeeper effect). Obviously if you are a self studier, just buy a good copy of old style Thomas (even has all the answers in the back.) If you check Amazon reviews, you can find the editions that are praised, for example. In general, people still like many Dover texts that are 50+ years old, so recency is not very important in lower level mathematics. (Be careful and read the reviews though).

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    $\begingroup$ A major factor to consider is the fact that many students are buying a homework system rather than a text. They only have the ebook to look at, and once the semester is done the service is gone and with it their ebook. It's sad really. My brother mentioned the trend to me recently, his corroborating evidence is the disappearance of used text buyers at his campus (before covid madness). So, the distinction between inclusion in the text and an online supplement starts to get less noticeable. In contrast, I expect book length may well grow as we separate from the need for physical publishing. $\endgroup$ Jan 9, 2022 at 22:40
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    $\begingroup$ If you look at the article I linked, it said that 77% of students wanted the physical book, not the e-book/HW system stuff. But the marketing departments of academic book publishers know that their target market is NOT the point of sale (student), but the point of specification (teacher, school). There's a reason why those companies make so much money, even when there should be a mass of lower priced textbooks. They are smart about influencing the gatekeepers. But academia is a racket in general. Massive amount of productive capital/time tied up there. $\endgroup$
    – guest
    Jan 10, 2022 at 1:39
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    $\begingroup$ of the students who care about education, the odds they are against e-homework systems is pretty high. Personally, I think there is no contest. Book homework with human graders is way way better when it is done well. But, the non-compliance of students with respect to due dates and the general unavailability of student graders for large sections is a real obstacle for the implementation of good homework. So, e-homework happens. And, selling the e-book with the homework system removes one other headache, the inevitable students who don't bother to get their textbook. In short... $\endgroup$ Jan 10, 2022 at 22:39
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    $\begingroup$ all the change in textbooks and math education is being driven by the most insincere students. In contrast, those who payed for an education and actually seek to attain it through hard work are given inferior products in the name of convenience. Of course, the inconvenience generated by careless students is real. I guess we could just fail them all, but... then that brings a whole other set of problems. $\endgroup$ Jan 10, 2022 at 22:42

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