Explanation of Algebraic Expressions - Succeed in Understanding Algebra. Also refer to numbers, variables, constants, operators, parentheses, grouping brackets, equation, sub-expression, mathematics, math, maths, Ron Kurtus, School for Champions. Copyright © Restrictions
Algebraic Expressions
by Ron Kurtus (revised 13 July 2008)
An expression in Algebra is a combination of numbers, variables, constants, operators and parentheses or grouping brackets that are stated as an entity. An equation consists of an expression on each side of the equals sign. Some expressions are made up of sub-expressions. Much of Algebra concerns simplifying expressions to facilitate the solution of equations.
Questions you may have include:
- What is the definition of expression?
- What are sub-expressions?
- How do you simplify expressions?
This lesson will answer those questions. There is a mini-quiz near the end of the lesson.
Definition of expressions
An expression consists of a combination of numbers, variables, constants, operators and/or parentheses. Examples include:
3
x
2y − 3
x2 + (4x + 2)/2
25 + (x + 3)3/2z − [5 + z(x+ 1) − 7]
Operator alone is not an expression
Although an individual number, variable or constant can be an expression, an operator by itself is not an expression. In other words, 3, x and c can be expressions, but + and ÷ are not expressions.
Expressions used in equations
An equation consists of an expression on each side of the equals sign.
The equation x2 + (3y + 2)/2 = 7z consists of the expressions x2 + (3y + 2)/2 and 7z.
Monomial and other expressions
An expression can be defined by the number of plus (+) or minus (−) signs it has, after it has been simplified.
Monomial
A monomial expression has one term and no plus or minus signs. Examples of monomials include:
2
7x
xy2z
Binomial
A binomial expression has two terms, with at least one variable or constant, and one plus (+) or minus (−) sign. Examples of binomials include:
x + 2
7x − 3y
xy2z/2 + 8
But note that 5x − 3x is not a binomial, because it simplifies to 2x.
A trinomial expression has three terms, with at least one variable or constant, and two plus (+) or minus (−) signs. Examples of trinomials include:
ax + y − 7
x + 2y + z
xy2z/2 − z + 8
Note that x3 − 15 + 8x3 is not a trinomial. It is really a binomial, since it can be simplified to: 9x3 − 15
Sub-expressions
An expression can consist of several expressions or sub-expressions.
For example, the expression 2y − 3 consists of sub-expressions 2y and 3. Also 2y consists of sub-expressions 2 and y.
Likewise, x2 + 2x + 1 consists of sub-expressions x2, 2x, and 1. And x2 consists of sub-expression x (since x2 is x times x). And 2x consists of sub-expressions 2 and x.
Exercise example
What are the expressions in the equation y + 1 = x2 + x(y + 1)?
Expressions on each side of the equation are y + 1 and x2 + x(y + 1)
Expressions in y + 1 are y and 1
Expressions in x2 + x(y + 1) are x2 and x(y + 1)
Expression in x2 is x
Expressions in x(y + 1) are x and (y + 1)
Expressions in (y + 1) are y and 1
Simplifying expressions
Expressions are meant to be used in equations. Thus, the expressions should be meaningful and in their simplest form to facilitate solving the equation. Much of Algebra concerns putting expressions in meaningful forms.
For example, the expression, x2 + (4x + 2)/2 can be reduced to x2 + 2x + 1 by completing the division by 2 in the expression (4x + 2)/2.
In some cases, it is useful to put an expression in a less simplified form, to facilitate the solution of an equation. For example, x2 + 2x could be factored into x(x + 2) to make it easier to solve the equation x2 + 2x = 0.
Summary
An expression is a combination of numbers, variables, constants, operators and parentheses or grouping brackets that are stated as an entity. An operator or grouping bracket alone is not an expression. An equation consists of an expression on each side of the equals sign. Some expressions are made up of sub-expressions.
Much of Algebra concerns simplifying expressions to facilitate the solution of equations.
See side menu for more Algebra topics
Be expressive when explaining things
Resources
The following resources provide information on this subject:
Websites
Books
Mini-quiz to check your understanding
If you got all three correct, you are on your way to becoming a Champion in Algebra. If you had problems, you had better look over the material again.
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Algebraic Expressions