Chapter 1'2 Variables in Algebra

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Chapter 1.2- Variables in Algebra

• Goals
• How to evaluate variable expressions
• How to represent real-life quantities using
  variable expressions
• WHY?
• You can use variables in algebra to represent
  numbers. These variables can be used to express
  number relationships, such as in the formula d
  rt for distance, rate, and time.

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Evaluating Variable Expressions

• A variable is a letter that is used to represent
  one or more numbers. The numbers are the values
  of the variable. An algebraic expression is a
  collection of numbers, variables, operations and
  grouping symbols

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Examples

• 8y
• 16a/b
• 4r t

• 8 times y
• 16 times a, then divided by b
• 4 times r, plus t
• When each variable in an algebraic expression is
  replaced by a number, we say that we are
  evaluating the expression, and the resulting
  number is the value of the expression

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Value of the Expression

• 4x when x 2
• 4(2) 8
• 5x 4y when x 3 and y 2
• 5(3) 4(2)
• Remember your Order of Operations!
• X (2x 1) when x 3
• You must replace all occurrences of x!

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Question?

• Is there a difference between 3x and x³?
• x x x 3x
• x x x x³
• Evaluate each expression at x 2

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Real Life Stuff

• Area of a Rectangle A lw
• Interest Earned I Prt
• I- interest, P- principal, r- interest rate, t-
  time
• Distance d rt
• Suppose you are traveling in a car at a constant
  speed of 75 miles per hour for 2 and one-half
  hours. How far will you travel?

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Assignment

• 1-6
• 9-16
• 25, 27, 28
• 40
• 43, 44