Evaluating Algebraic Expressions

Evaluate Evaluate has the word “valu” hidden inside When you see the word “evaluate” – you know that your answer is going to be a value. Let’s try one. Evaluate 2xy – 3yz if x = 2, y = 5, and z = -3

To evaluate this algebraic expression, 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. Bird’s nesting

I’m going to rewrite the expression, but every time I get to a letter, I’m going to insert an open ( ) instead. Those are the proverbial birds’ nests. 2( )( ) – 3( )( ) Evaluate 2xy – 3yz if x = 2, y = 5, and z = -3

Let’s meet our little feathered friends! x = 2, y = 5, and z = -3 And fly them into their nests 2xy – 3yz = 2( )( ) – 3( )( ) 2( 2 )( 5 ) – 3( 5 )( -3 ) 4( 5 ) -15( -3 ) ( 2 ) = 4 -3( 5 ) = ( -3 ) = +45 See how the ( ) keeps everything straight!

Evaluating Algebraic Expressions Expect a value for your answer. Replace all the letters with ( ) Fly the ‘birds’ into their ‘nests’ (be careful to get the right bird into the right nest!). Follow the order of operations and the rules of signed numbers.