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Functions & points

Q:  Evaluate f(3) for each of the following:

a) (1,2) (2,0) (3,1) (4,2)

b) (1,2) (2,3) (3,4) (4,5)

A:  Something to remember about functions… The general notation is “f(x)”.  So, if I ask for f(3), I am implying that x is 3.  Notice that the 3 took the place of the x?  Basically:

f(3) means:  plug in 3 for x and what is the y value?  Or, which number “pops up” when x = 3.

Answer for part A:  Notice that these are all (x, y) points… Which point has x=3?  That is the point (3, 1).  So, f(3) = 1.

Answer for part B:  x = 3 at the point (3,4).  So, f(3) = 4.

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