Algebra 1: Expressions, Equations, and Applications

Algebra 1: Expressions, Equations, and Applications by Paul A. Foerster. hardcover edition. ISBN: 9780201324587.

You are about to embark on the course which lays the foundation for virtually all of higher mathematics. In previous courses you have occasionally used a letter to stand for a number you seek to find. Now you will be less concerned about what number the letter represents, and will concentrate on things that are true just because it is a number. The letters used will be called variables, because they can stand for different numbers at different times. Expressions containing these variables can represent quantities in the real world, such as how high a ball is above the ground at various times after it was thrown. By learning how to operate with such expressions, you will be able to predict such things as how to operate with such expressions, you will be able to predict how high the ball is at a given time, how long it takes to reach a given height, and when it will be back down.