Expert: Paul Klarreich - 10/15/2007

Question
f (x) = x2 - 7x + 10; find (a) f (0), (b) f (5), and (c) f (-2).

Answer
Questioner:   Patty
Category:  Advanced Math
Private:  No
 
Subject:  help

<< That's not a useful subject line. I changed it.

Question:  f(x) = x2 - 7x + 10; find (a) f(0), (b) f(5), and (c) f(-2).
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Hi, Patty,

Welcome to precalc and function notation.  Here is the big clue:

ALWAYS PARENTHESIZE FUNCTION NOTATION.

Take a piece of paper NOW and write that sentence 100 times.

Each of these examples is done the same way:

1. Write the pattern you are given:  That is what you have -- a PATTERN.

f(x) = x^2 - 7x + 10

(That's how to write exponents on the computer --  x^2.)

2. Write it over, using EMPTY PARENTHESES for the argument symbol, which is 'x' in this example.

f( ) = ( )^2 - 7( ) + 10

3. INSERT the substitution value and do the calculation:

f(0) = (0)^2 - 7(0) + 10
f(0) = 0 - 0 + 10
f(0) = 10
. . . . . . . . . . . .
f(5) = (5)^2 - 7(5) + 10
f(5) = 25 - 35 + 10
f(5) = - 10 + 10
f(5) = 0
. . . . . . . . . . . .
f(-2) = (-2)^2 - 7(-2) + 10
f(-2) = 4 + 14 + 10
f(-2) = 28