Using Function Notation

Independent and Dependent Variables Independent Variable Will change no matter what The first member of the ordered pair Domain x Dependent Variable Changes depend on the independent variable The second member of the ordered pair Range y

Function Notation You use the symbol f(x) in place of y Function notation allows you to see the input value.

An Example If f(x) = 2x + 8, find f(-2) Replace x with –2 on the right and simplify: f(-2) = 2(-2) + 8 f(-2) = -4 + 8 f(-2) = 4

Another Example If g(a) = -3a – 5, find g(-1). Replace a in the function rule with –1 and simplify. g(-1) = -3(-1) – 5 g(-1) = 3 – 5 g(-1) = -2

Another Example If f(x) -

Using a Table of Values You can write a rule for a function by analyzing a table of values. Ask yourself “What did I do to the x-values to get the y-values?”

Another Way From a table Find the differences between the values in the x column (independent variable) Find the differences in the values in the y coulmn (dependent variable) If there is a constant difference in each, divide the y differences by the x differences That quotient will be the number multiplied by “x”

Another Way From a table So you have y = x. What else do you have to do to that to get the number in the y column? (Usually add or subtract something.)

Tables of Values 2 1 1 y = 1x ? 2 ÷ 2 = 1 1 ÷ 1 = 1 y = 1x ? y = x + 2

Try these…

Try these…-answers f(x) = -x + 20 f(x) = 3x

Try these… For f(x) = 4x – 9, find f(x) when x = 3 and x = 5. For g(x) = 1/3x - 10 find g(27) and g(-15) Identify the independent variable: The cost to wrap an order is $3 plus $1 per item wrapped. Identify the dependent variable: Tabor charges $25 for each lawn he mows.

Try these…answers For f(x) = 4x – 9, find f(x) when x = 3 and x = 5. 3 and 11 For g(x) = 1/3x - 10 find g(27) and g(-15) -1 and -15 Identify the independent variable: The cost to wrap an order is $3 plus $1 per item wrapped. Number of items Identify the dependent variable: Tabor charges $25 for each lawn he mows. Amount earned