Variable expressions are mathematical phrases that contain numbers, operations, and variables. A variable is a symbol (usually a letter) that represents an unknown value.
Think of variables as empty boxes that can hold different values. The expression changes its value depending on what number you put in the box.
To evaluate a variable expression means to substitute a given number for the variable and then calculate the value of the expression using the correct order of operations.
Always rewrite the expression after substituting the value for the variable. This helps prevent calculation errors.
Variable expressions can include all four basic operations: addition, subtraction, multiplication, and division. The process for evaluation remains the same regardless of which operations are used.
In algebra, we often write multiplication without the × symbol. For example, 4n means 4 × n, and 2(5) means 2 × 5.
When expressions contain more than one operation, you must follow the order of operations to evaluate them correctly.
Remember PEMDAS: Parentheses first, then Exponents, then Multiplication and Division (left to right), and finally Addition and Subtraction (left to right).
Some expressions contain more than one variable. When evaluating these expressions, substitute the appropriate value for each variable.
When an expression has multiple variables, make sure you substitute the correct value for each variable. Different variables can have different values.
Variable expressions are used to represent real-world situations where quantities can change. Evaluating these expressions helps solve practical problems.
When solving word problems, identify what the variable represents and what operation(s) to use before evaluating the expression.