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2-1 Variables and Expressions th 6 Grade Math HW: Page 50 #5-17 all Course 1 2-1 Variables and Expressions Who did not take the Chapter 1 Test? Course 1 2-1 Variables and Expressions Warm Up Problem of the Day Lesson Presentation Course Course 11 2-1 Variables and Expressions Warm Up Simplify. 1. 2. 3. 4. Course 1 4+731 87 15 5 6(9 + 2) + 7 35 7 5 24 84 73 25 2-1 Variables and Expressions Problem of the Day How can the digits 1 through 5 be arranged in the boxes to make the greatest product? 4 Course 1 3 5 1 2 2-1 Variables and Expressions Today’s Learning Goal Learn to identify and evaluate expressions. Course 1 2-1 Variables and Expressions Vocabulary variable constant algebraic expression Course 1 2-1 Variables and Expressions A variable is a letter or symbol that represents a quantity that can change. A constant is a quantity that does not change. Course 1 2-1 Variables and Expressions An algebraic expression contains one or more variables and may contain operation symbols. p 7 is an algebraic expression. Algebraic Expressions 150 + y 35 w + z NOT Algebraic Expressions 85 ÷ 5 10 + 3 5 To evaluate an algebraic expression, substitute a number for the variable and then find the value. Course 1 2-1 Variables and Expressions Additional Example 1A: Evaluating Algebraic Expressions Evaluate the expression to find the missing values in the table. Substitute for y in 5 y. y 5y 16 80 y = 16; 5 16 = 80 27 135 y = 27; 5 27 = 135 35 175 y = 35; 5 35 = 175 The missing values are 135 and 175. Course 1 2-1 Variables and Expressions Additional Example 1B: Evaluating Algebraic Expressions Evaluate the expression to find the missing values in the table. Substitute for z in z 5 + 4. z z5+4 20 8 z = 20; 20 5 + 4 = 8 45 13 z = 45; 45 __ 5 + 4 = 13 __ 60 16 z = 60; 60 __ 5 + 4 = 16 __ The missing values are 13 and 16. Course 1 2-1 Variables and Expressions Try This: Example 1A Evaluate the expression to find the missing values in the table. Substitute for x in x 9. x x9 18 2 x = 18; 18 9 = 2 36 4 x = 36; 36 9 = 4 54 6 x = 54; 54 9 = 6 The missing values are 4 and 6. Course 1 2-1 Variables and Expressions Try This: Example 1B Evaluate the expression to find the missing values in the table. Substitute for z in 8 z + 2. z 8z+2 7 58 z = 7; 8 7 + 2 = 58 9 74 z = 9; 8 __+ 9 2 = __ 74 11 90 z = 11; 8 __ 11 + 2 = __ 90 The missing values are 74 and 90. Course 1 2-1 Variables and Expressions Multiplication and division can be written without using the symbols and . Instead of . . . x3 35 ÷ y You can write . . . x3 x(3) 3x 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.” Course 1 2-1 Variables and Expressions Additional Example 2A: Finding an Expression Find an expression for the table. n n 13 39 3 39 13 = 3 52 4 52 13 = 4 65 5 65 13 = 5 An expression is n 13, or n . 13 Course 1 2-1 Variables and Expressions Additional Example 2B: Finding an Expression Find an expression for the table. p 7•p 4 28 7 • 4 = 28 6 42 7 • 6 = 42 8 56 7 • 8 = 56 An expression is 7 • p, or 7p. Course 1 2-1 Variables and Expressions Try This: Example 2A Find an expression for the table. u u3 21 7 21 3 = 7 42 14 42 3 = 14 63 21 63 3 = 21 An expression is u 3, or Course 1 u. 3 2-1 Variables and Expressions Try This: Example 2B Find an expression for the table. n 4•n 5 20 4 • 5 = 20 8 32 4 • 8 = 32 11 44 4 • 11 = 44 An expression is 4 • n, or 4n. Course 1 2-1 Variables and Expressions Lesson Quiz: Part 1 1. Evaluate each expression to find the missing values in the tables. 2. Find an expression for the table. x x–5 10 5 7 2 5 0 x 7x 1 7 3 21 35 5 Course 1 2-1 Variables and Expressions Lesson Quiz: Part 2 3. Evaluate 8x for x = 5. 40 4. Evaluate 4x – 1 for x = 12. 47 Course 1