1. Evaluating Functions

2. Evaluating Functions
Evaluating functions is just like evaluating algebraic expressions.
Evaluate has the word “valu” hidden inside.
When you see the word “evaluate” – you know that your answer is going to be a value.

3. is just another way of saying
Evaluating Functions
The only difference with functions is that the ‘notation’ (the way it is written) is different.
f ( x ) = x find f ( - 2 )
is just another way of saying
y = x + 3 find y when x = - 2

4. Evaluating Functions Actually, function notation is easier.
Even if you didn’t know anything about it,
it sort of looks like they
put the - 2 where the x was!
f ( x ) = x find f ( - 2 )

5. Bird’s nesting
To evaluate this function, we’re going to use a technique that I call “bird’s nesting”. It may sound silly but it will save you a world of hurt when it comes to sign mistakes.

6. f ( x ) = x find f ( - 2 )
I’m going to rewrite the expression, but every time I get to a letter, I’m going to insert an open ( ) instead - the proverbial bird’s nest. f ( - 2 ) = ( ) + 3

7. See how the ( ) keeps everything straight!
Now let’s fly our little feathered friend into his nest!
f ( - 2 ) = (- 2 ) + 3
f (- 2 ) = 1
See how the ( ) keeps everything straight!

8. Evaluating Functions Expect a value for your answer.
Replace all the letters with ( )
Fly the ‘bird’ into its ‘nest’.
Follow the order of operations and the rules of signed numbers.