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Variables and Expressions

Variables and Expressions. Lesson 2-2. Vocabulary. A numerical expression is a mathematical phrase with only numbers and operation symbols (+, -, x, ÷). Example: 8 + 5 - 2. An algebraic expression is a mathematical phrase that contains a variable and operation symbols.

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Variables and Expressions

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  1. Variables and Expressions Lesson 2-2

  2. Vocabulary A numerical expression is a mathematical phrase with only numbers and operation symbols (+, -, x, ÷). Example: 8 + 5 - 2 An algebraic expression is a mathematical phrase that contains a variable and operation symbols. A variable is a symbol (usually a letter) that stands for a number. Algebraic expression: 5y + 2

  3. Evaluating Numerical Expressions • Use PEMDAS (order of operations). 84 – 10 ÷ 2 84 – 5 79

  4. Evaluating Algebraic Expressions • Replace the variable with the value that you are given. • Now we have a numerical expression. • Solve using order of operations.

  5. Example: Evaluate 2b-8 for b=11 2b-8 2(11)-8 Substitute the 11 for the variable. 22 - 8 Multiplying comes before subtracting. 14

  6. Example 2: Evaluate 5x-y for x=12 and y=14 5x-y 5(12) - 14 60 - 14 46

  7. Homework Time

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