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Variables and Expressions
Lesson 2-2
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Vocabulary A numerical expression is a mathematical phrase with only numbers and operation symbols (+, -, x, ÷). Example: 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
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Evaluating Numerical Expressions
Use PEMDAS (order of operations). 84 – 10 ÷ 2 84 – 5 79
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Evaluating Algebraic Expressions
Replace the variable with the value that you are given. Now we have a numerical expression. Solve using order of operations.
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Example: Evaluate 2b-8 for b=11
2(11)-8 Substitute the 11 for the variable. 22 - 8 Multiplying comes before subtracting. 14
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Example 2: Evaluate 5x-y for x=12 and y=14
5(12) - 14 46
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