January 2019
Beginner
400 pages
10h 21m
English
Content preview from Algebra II For Dummies, 2nd Edition
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.
Chapter 19
Ten Special Types of Numbers
IN THIS CHAPTER
Associating numbers with shapes
Characterizing numbers as perfect, narcissistic, and so on
Mathematicians classify numbers in many ways, much like psychologists (and gossipers) classify people: even or odd, positive or negative, rational or irrational, and so on. In this chapter, I show you even more ways to pigeonhole numbers by putting them into interesting groupings that make them special.
Triangular Numbers
Triangular numbers are numbers in the sequence 1, 3, 6, 10, 15, 21, 28, and so on (for more on sequences, see Chapter 16). You may have noticed that each term in the sequence is larger than the previous number by one more value than the previous difference between the terms. Say what? Okay, let me put that another way: To find the second term, you add 2 to the previous term. To find the third term, you add 3; add 4 for the fourth term, 5 for the fifth, and so on.
The formula for finding the nth triangular number is 
. Here’s how you use the formula to find the eighth triangular number (one more than the number 28 in the previous list): . The number 36 is 8 more than the number 28, which is 7 more than 21, and so on. ...
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.
Read now
Unlock full access
More than 5,000 organizations count on O’Reilly
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.