Evaluating Functions

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.

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 + 3 find f ( - 2 ) is just another way of saying y = x + 3 find y when x = - 2

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 + 3 find f ( - 2 )

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.

f ( x ) = x + 3 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

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!

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.