7th Grade Math

384 Linear Functions

A function that is written as an equation can also be written in a form called

function notation. Consider the equation y = 4 x.

Equation Function notation

y = 4 x f (x) = 4 x

The variable y and f (x) both represent the dependent variable. To find

the value of the function for a certain input, substitute the input for the

variable x.

Find f (3) if f (x) = 5 x.

f (x) = 5 x Write the function.

f ( 3 ) = 5 (3) Substitute 3 for x into the function rule.

So, f (3) = 15.

The function notation,

f (x) is read f of x.

Determine whether each relation is a function. Explain.

26. 
    

    {(4, 12), (5, 16), (5, 17), (6, 10)} 27. {(8, 8), (9, 9) , (10, 10), (11, 11)}

    
    


27. 
    

    (^) x 25811
    y 3357

    
    


28. 
    

    x 12 16 20 12
    y 4 8 12 16

    
    


29. 
    

    y

    
    

0 x

31. y

0 x

Find the value of each function.

32. f (4) if f (x) = 2 x 33. f (-5) if f (x) = 20 x 34. f (-8) if f (x) = - 5 x + 10

Determine a rule for each set of ordered pairs. Then copy and complete each function table.

35. (^) x? f (x)
    2 - 1
    4 1
    6 3
    8


36. (^) x? f (x)
    1 3
    2 7
    3 11
    4


37. (^) x? f (x)
    0 6
    1 8
    3 12
    5
    377_384_C07_L1_895130.indd 384 12/31/09 4:23 PM