Algebra is chock-full of words that are useful but often misunderstood. To do well on the ACT Math test, you should be able to define these important terms: variable, constant, equation, expression, term, and coefficient.
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Variable. A variable is any letter that stands for a number. The most commonly used letters are x and y, but you can use any letter.
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Constant. A constant is a number without a variable. For example: The equation 6m + 7 = –m has one constant, the number 7.
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Equation. An equation is any string of numbers and symbols that makes sense and includes an equal sign. For example, here are three equations:
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Expression. An expression is any string of numbers and symbols that makes sense when placed on one side of an equation. For example, here are four expressions:
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Term. A term is any part of an expression that’s separated from the other parts by either a plus sign (+) or a minus sign (–). Important: A term always includes the sign that immediately precedes it. For example,
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The expression 3x – 7 has two terms: 3x and –7.
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The expression –x2 – 9x + 11 has three terms: –x2, –9x, and 11.
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The expression
has one term:
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Coefficient. A coefficient is the numerical part of a term, including the sign that precedes it (+ or –). Important: Every term has a coefficient. When a term appears to have no coefficient, its coefficient is either 1 or –1, depending on the sign. For example,
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The term 3x has a coefficient of 3.
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The term –9x has a coefficient of –9.
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The term –x2 has a coefficient of –1.
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Being clear about the meanings of these six words can help you with any other math you study.
