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7th Grade Math / Lesson 3: Equivalent Expressions

Equivalent Expressions
What will we be learning in this lesson?


  • In this lesson, you will look at one way to determine if two expressions represent the same thing (if they are equivalent).

    Vocabulary words are found in this purple color throughout the lesson. Remember to put these in your notebook.


Equivalent Expressions
 


  • Sometimes, parts of problems look different, but they really aren't. In this section, we will look at how to determine if two pieces of a problem that look different are actually represent the same thing.
  • The parts that we will look at are called expressions (they contain variables, numbers, and operations).
  • Take the following expressions:
4x + 2       and        4 + x + 2
  • Do these expressions represent the same thing (amount)?
 
 


Equivalent Expressions
 

4x + 2       and        4 + x + 2
  • To determine if these expressions represent the same thing, we will pick a number and test it in both expressions.
  • Say we choose the number 3. Put 3 in for the variable in each expression. Remember, 4x means 4*x. In other words 4 times x.
 
The answers are not equal to each other, therefore,   
the two expressions are not equivalent.
 


Equivalent Expressions
 

  • Try another pair of expressions.
3x - 1        and        x + x + x - 1  
  • Let's try the number 2 this time. If the two expressions end up equal, the expressions are equivalent to each other.
 
The answers are equal to each other, therefore,   
the two expressions are equivalent to each other.
Any value that you would use for x would give you equal answers.


  • Can you determine if two expressions are equivalent to one another?

  • Be sure to go back to your classroom to get any homework assignments or other activities you need to attend to.