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Algebraic expressions are made up of terms. A term can be a single number, a variable, or numbers and variables multiplied together. For example, in the expression \(7a - 9b\), the terms are \(7a\) and \(-9b\).

Terms in an algebraic expression are separated by plus or minus signs. It’s important to identify each term correctly because each term tells us something about the expression's different parts.

Understanding terms is the first step in understanding any algebraic expression. It helps break down complex expressions into manageable parts, making it easier to work with.

Each term in an algebraic expression is made up of coefficients and variables. The coefficient is the number that is multiplied by the variable. In the expression \(7a - 9b\):

- The term \(7a\) has a coefficient of 7 and a variable \(a\).
- The term \(-9b\) has a coefficient of \(-9\) and a variable \(b\).

Coefficients tell us how many times to multiply the variable. They can be positive or negative. The variable represents an unknown quantity that can change. In algebra, we often use letters like \(a, b, x, y\) to stand for variables.

Understanding coefficients and variables helps to solve and manipulate algebraic expressions correctly. It’s crucial to know which part of the term tells us the quantity and which part tells us what’s being counted or measured.

Subtraction in algebra works similarly to arithmetic subtraction. However, it's crucial to pay attention to the signs of the terms:

- In the expression \(7a - 9b\), the subtraction sign indicates that \(9b\) is being subtracted from \(7a\), making the second term \(-9b\).

When subtracting algebraic expressions, you must combine like terms - terms with the same variable raised to the same power. For example, \(7a - 3a\) simplifies to \(4a\).

Paying attention to the signs and coefficients of each term allows us to correctly interpret and manipulate algebraic expressions through subtraction. This understanding is essential for further algebraic operations like solving equations and simplifying expressions.