1. Functions 2.1 (A)

2. What is a function?
Rene Descartes (1637) – Any positive integral power of a variable x.
Gottfried Leibniz ( ) – Any quantity associated with a curve
Leonhard Euler ( ) – Any equation with 2 variables and a constant
Lejeune Dirichlet ( ) – Rule or correspondence between 2 sets

3. What is a relation? Step Brothers? Math Definition
Relation: A correspondence between
2 sets
If x and y are two elements in these sets, and if a relation exists between them, then x corresponds to y, or y depends on x
x  y or (x, y)

4. Example of relation
Names Grade on Ch. 1 Test Buddy A Jimmy B Katie C Rob

5. Dodgeball Example Say you drop a water balloon off the top of a 64 ft.
building. The distance (s) of the dodgeball from the ground after t seconds is given by the formula:
Thus we say that the distance s is a function of the time t because:
There is a correspondence between the set of times and the set of distances
There is exactly one distance s obtained for any time t in the interval

6. Def. of a Function
Let X and Y be two nonempty sets. A function from X into Y is a relation that associates with each element of X exactly one element of Y.
Domain: A pool of numbers there are to choose from to effectively input into your function (this is your x-axis). 
The corresponding y in your function is your value (or image) of the function at x.
Range: The set of all images of the elements in the domain (This is your y-axis)

7. Domain/Range Example
Determine whether each relation represents a function. If it is a function, state the domain and range.
a) {(1, 4), (2, 5), (3, 6), (4, 7)}
b) {1, 4), (2, 4), (3, 5), (6, 10)}
c) {-3, 9), (-2, 4), (0, 0), (1, 1), (-3, 8)}

8. Practice
Pg. 96 #2-12 Even

9. Function notation Given the equation Replace y with f(x)
f(x) means the value of f at the number x
x = independent variable
y = dependent variable

10. Finding values of a function
For the function f defined by
evaluate;
a) f(3)
b) f(x) + f(3)
c) f(-x)
d) –f(x)
e) f(x + 3) f)

11. Practice 2
Pg. 96 #14, 18, 20

12. Implicit form of a function
Explicit Form

13. Determine whether an equation is a function

14. Finding the domain of a function
Find the domain of each of the following functions:

15. Tricks to Domain
Rule #1 If variable is in the denominator of function, then set entire denominator equal to zero and exclude your answer(s) from real numbers. Rule #2 If variable is inside a radical, then set the expression greater than or equal to zero and you have your domain!

16. Practice 3
Pg. 96 #22-46 E