2-2 Expressions and Equations Explained
Key Concepts of Expressions and Equations
Expressions and equations are fundamental components in algebra. Understanding the difference between them and how to manipulate them is crucial for solving mathematical problems.
1. Expressions
An expression is a combination of numbers, variables, and mathematical operations (such as addition, subtraction, multiplication, and division) without an equal sign. Expressions can be simplified but not solved.
Example:
\[ 3x + 5 \]
This is an expression because it does not have an equal sign.
2. Equations
An equation is a statement that two expressions are equal. It contains an equal sign and can be solved to find the value of the variable.
Example:
\[ 3x + 5 = 14 \]
This is an equation because it has an equal sign and can be solved for \( x \).
3. Simplifying Expressions
Simplifying an expression involves performing all possible operations to reduce the expression to its simplest form. This often involves combining like terms and using the order of operations (PEMDAS/BODMAS).
Example:
Simplify \( 4x + 7 - 2x + 3 \):
Combine like terms: \( 4x - 2x + 7 + 3 = 2x + 10 \).
4. Solving Equations
Solving an equation involves finding the value of the variable that makes the equation true. This is done by isolating the variable on one side of the equation.
Example:
Solve \( 3x + 5 = 14 \):
Subtract 5 from both sides: \( 3x = 9 \).
Divide both sides by 3: \( x = 3 \).
5. Combining Like Terms
Combining like terms is a method used to simplify expressions by adding or subtracting terms that have the same variable and exponent.
Example:
Combine like terms in \( 5x^2 + 3x - 2x^2 + 4 \):
Combine \( 5x^2 \) and \( -2x^2 \): \( 3x^2 \).
The simplified expression is \( 3x^2 + 3x + 4 \).
6. Distributive Property
The distributive property is used to simplify expressions and solve equations by distributing a factor across a sum or difference.
Example:
Use the distributive property to simplify \( 3(2x + 4) \):
Distribute 3: \( 3 \times 2x + 3 \times 4 = 6x + 12 \).
Practical Applications
Understanding expressions and equations is essential for solving real-world problems. For instance, calculating the cost of items with discounts, determining the area of a rectangle, or solving for the unknown in a physics formula all involve expressions and equations.
Example:
If a store offers a 20% discount on a $50 item, you can set up an equation to find the final price:
Let \( x \) be the final price after the discount:
\[ x = 50 - 0.20 \times 50 \]
Simplify: \( x = 50 - 10 = 40 \).
The final price is $40.