# Algebra: Writing Expressions, Equations & Inequalities

Created 3 years ago

Duration 0:09:20
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Slide Content
1. ### Slide 1 - Introduction to Algebra

• Writing Expressions, Equations & Inequalities
2. ### Slide 2 - What is algebra?

• Al · ge · bra
• (noun) the part of mathematics in which letters and other general symbols are used to represent numbers and quantities.

4. ### Slide 4 - Variables & Constants

• Variables: a quantity that could change (or vary) during the calculations. In this class, a variable can be represented by any lower case letter (but it’s best to avoid o and l)
• Constant: a quantity that will not change (is constant) during the calculations. This shows up as a number.
5. ### Slide 5 - Coefficients & Operators

• Coefficients: constants that come before a variable. They tell us how many of that variable are present. For example “four x’s” is written 4x
• Operators: mathematical symbols that represent operations to be performed (adding, subtracting, etc.)
6. ### Slide 6 - Expressions & Equations

• Expressions and equations are like mathematical sentences.
• An expression has no equals sign, but an equation does…
• For example:
• “Four of a number added to 10”
• 4n + 10  this is an expression
• Another example:
• “Four of a number added to 10 is 30”
• 4n + 10 = 30  this is an equation
• Notice that “a number” is shown as a variable in the examples. We don’t know what that number is yet, so we write is as a variable. When we read an expression or equation, we say “a number” outloud.
7. ### Slide 7 - Equations & Inequalities

• An equation has an equal sign. An inequality has an inequality sign.
• ≥ “greater than or equal to”
• > “greater than” (but not equal to)
• ≠ “not equal to”
• < “less than” (but not equal to)
• ≤ “less than or equal to”
• Example:
• Read from left to right:
• “a number is greater than five”
• Notice that the larger part of the sign points to the larger amount (or “the alligator eats the bigger meal”)
8. ### Slide 9 - Evaluating Expressions

• When we are given an expression and a solution, we can evaluate that expression for the given solution.
• Example:
9. ### Slide 11 - Mentally Solving Equations

• Equations can be solved mentally use “try, check, revise”.
• Step 1. Read aloud: “12 minus a number is 10”
• Step 2. Estimate a solution and try it: “Two? 12 minus 2 is 10” CHECK!
10. ### Slide 13 - Mentally Solving Inequalities

• Inequalities can also be solved mentally use “try, check, revise”.
• Step 1. Read aloud: “A number is less than 20”
• Step 2. Estimate a solution and try it: “Fifteen? 15 is less than 20?” CHECK!