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**HallsofIvy** There are at least two different definitions of "linear" function. In basic algebra and pre-calculus, it is common to refer to any function having a straight line as graph, which can always be written y= mx+ b, as "linear". That would include m= 0, y= a constant.

In linear algebra, a linear transformation is a function satisfying f(ax+ by)= af(x)+ bf(y). For real numbers, that is of the form f(x)= mx with "constant part" 0. Of course, even in that case f(x)= 0 with both m and b equal to 0, would be "constant" linear function.

What was the title of this textbook, what course was it for, and **exactly** what did it say?