AF1.2 Use the correct order of operations to evaluate algebraic expressions. Section 1.1 Evaluating Algebraic Expressions Evaluate each expression for the given value of the variable. x + 5 for x = 11 Substitute 11 for x Add 16 2a + 3 for a = 4 Substitute 4 for a2(4) + 3 Multiply8 + 3 Add11 What is the meaning of the word variable in the following context? "The air temperature in the desert was quite variable yesterday; it was cold overnight and warm during the day." Teacher: What is 7Q plus 3Q? Student: 10Q Teacher: You're Welcome!

5x + 2y for x = 13 and y = 11 5(13) + 2(11)Substitute 13 for x and 11 for y Multiply 87Add p(24 - q) for p = 8 and q = 17 8( )Substitute 8 for p and 17 for q 8(7)Simplify within parentheses. 56Mulitply

If c is a temperature in degrees Celsius, then 1.8c + 32 can be used to find the temperature in degrees Fahrenheit. Convert each temperature from degrees Celsius to degrees Fahrenheit. freezing point of water: 0 0 C highest recorded temperature in the United States: 57 0 C Show how to work the problem here.

Practice problems. Evaluate each expression x + 7 for x = 237t + 2 for t = z - 3y for x = 1.5, y =6, z = 23 51

Think and Discuss 1.Give an example of a numerical expression and of an algebraic expression. 2.Tell how to evaluate an algebraic expression for a given value of a variable. 3.Explain why you cannot find a numerical value for the expression 4x - 5y for x = 3. Write three examples of variables (quantities that change value) from your everyday life.

Math Background Francois Viete ( ) was a lawyer in France who devoted his spare time to mathematics. In his book, In Artem, he introduced the idea of representing unknown quantities using vowels and constants using constants. He also used our present symbols + and - but had no symbol for equality. To write "equals" he would use the Latin word aequatur. Viete is sometimes called the Father of Algebra.