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Learn to identify and evaluate expressions .

Learn to identify and evaluate expressions. Vocabulary. variable constant algebraic expression evaluate. A variable is a letter or symbol that represents a quantity that can change. A constant is a quantity that does not change. Algebraic Expressions. NOT Algebraic Expressions.

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Learn to identify and evaluate expressions .

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  1. Learn to identify and evaluate expressions.

  2. Vocabulary variable constant algebraic expression evaluate

  3. A variable is a letter or symbol that represents a quantity that can change. A constant is a quantity that does not change.

  4. Algebraic Expressions NOT Algebraic Expressions An algebraic expression contains one or more variables and may contain operation symbols. So p 7 is an algebraic expression. 150 + y 85 ÷ 5 35 w + z 10 + 3 5 To evaluate an algebraic expression, substitute a number for the variable and then find the value.

  5. y 5 y 16 80 y = 27; 5  = 27 35 y = 35; 5  = Additional Example 1A: Evaluating Algebraic Expressions Evaluate the expression to find the missing values in the table. Substitute for y in 5 y. y = 16; 5  16 = 80 27 135 135 175 35 175 The missing values are 135 and 175.

  6. z  5 + 42 z Substitute for z in z 5 + 42. 20 20 45 60 Additional Example 1B: Evaluating Algebraic Expressions Evaluate the expression to find the missing values in the table. z = 20; 20  5 + 16 = 20 25 z = 45; __  5 + 16 = __ 45 25 60 28 z = 60; __  5 + 16 = __ 28 The missing values are 25 and 28.

  7. x x  9 18 2 x = 36;  9 = 36 x = 54;  9 = 54 Check It Out: Example 1A Evaluate the expression to find the missing values in the table. Substitute for x in x  9. x = 18; 18  9 = 2 4 36 4 6 54 6 The missing values are 4 and 6.

  8. z 8z + 23 Substitute for z in 8  z + 23. 7 64 9 11 Check It Out: Example 1B Evaluate the expression to find the missing values in the table. z = 7; 8  7 + 8 = 64 9 80 z = 9; 8  __+ 8 = __ 80 11 96 z = 11; 8  __ + 8 = __ 96 The missing values are 80 and 96.

  9. Instead of . . . You can write . . . 35 y Writing Math When you are multiplying a number times a variable, the number is written first. Write “3x” not “x3.” Read 3x as “three x.” You can write multiplication and division expressions without using the symbols  and . x 3 x(3) 3x x 3 35 ÷ y

  10. Additional Example 2: Evaluating Expressions with Two Variables A rectangle is 4 units wide. How many square units does the rectangle cover if it is 3, 4, 5, or 6 units long? Make a table to help you find the number of square units for each length. 3 x 4 = square units 12 16 4 x 4 = square units 16 20 5 x 4 = square units 20 24 6 x 4 = square units 24 The rectangle will cover 12, 16, 20, or 24 square units.

  11. Check It Out: Example 2 A rectangle is 3 units wide. How many square units does the rectangle cover if it is 2, 3, 4, or 5 units long? Make a table to help you find the number of square units for each length. 2 x 3 = square units 6 9 3 x 3 = square units 9 12 4 x 3 = square units 12 15 5 x 3 = square units 15 The rectangle will cover 6, 9, 12, or 15 square units.

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