Why do some equations have one solution, others two or even more solutions and some no solutions? Why do we sometimes need to ""switch"" the direction of an ine

Are sequences functions? Why can’t the popular “vertical line test” be applied in some cases to determine if a relation is a function? How does the idea o

How does working with data in statistics differ from working with numbers in mathematics? What is variability, and how can we describe and measure it? How can w

"A series for teaching mathematics."--P. [1] of cover.