**Calculus Of One Real Variable**

Recall from algebra
that a function *f* is a rule that assigns to each real number *x* in its domain a unique real number *f*(*x*) in its

range. Strictly speaking, *f* is the function and *f*(*x*) is the value of the function *f* at *x*. However, we sometimes loosely refer to

*f*(*x*), or *y* if *y* = *f*(*x*), as the function.