Cracking The SAT Premium

FUNCTION FUNDAMENTALS

Think of a function as just a machine for producing ordered pairs. You put in one number and the machine
spits out another. The most common function is an f(x) function. You’ve probably dealt with it in your
algebra class.

Let’s look at a problem.

3.If    f(x)    =   x^3     –   4x  +   8,  then    f(5)    =

A) 67

B) 97

C) 113

D) 147

Here’s How to Crack It

Any time you see a number inside the parentheses, such as f(5), plug in that number for x. The question is
actually telling you to plug in! Let’s do it:

f(5)    =   5^3     –   4(5)    +   8

f(5)    =   125 –   20  +   8

f(5)    =   113

That’s (C).

What’s  This?

Anytime you see the nota-

tion    f(x),   know    that    f   isn’t

a   variable.   It’s    the name

of  the function.   When    you

say it  out loud    it’s    “f  of

x.” Though  f(x)    is  the most

common  way to  show    that

an  equation    is  a

mathematic  function,   any

letter  can be  used.   So  you

may see g(x)    or  h(d).   Know

that    you’re  still   dealing

with    a   function.

Try this next one:

14.If   f(x)    =   x^2     +   2,  which   of  the following   could   be  a   value   of  f(x)    ?

A) –1