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This module is from Fundamentals of Mathematics by Denny Burzynski and Wade Ellis, Jr. This module discusses algebraic expressions. By the end of the module students should be able to recognize an algebraic expression, be able to distinguish between terms and factors, understand the meaning and function of coefficients and be able to perform numerical evaluation.

Section overview

  • Algebraic Expressions
  • Terms and Factors
  • Coefficients
  • Numerical Evaluation

Algebraic expressions

Numerical expression

In arithmetic, a numerical expression results when numbers are connected by arithmetic operation signs (+, -, ⋅ , ÷). For example, 8 + 5 size 12{8+5} {} , 4 9 size 12{4 - 9} {} , 3 8 size 12{3 cdot 8} {} , and 9 ÷ 7 size 12{9 div 7} {} are numerical expressions.

Algebraic expression

In algebra, letters are used to represent numbers, and an algebraic expression results when an arithmetic operation sign associates a letter with a number or a letter with a letter. For example, x + 8 size 12{x+8} {} , 4 y size 12{4 - y} {} , 3 x size 12{3 cdot x} {} , x ÷ 7 size 12{x div 7} {} , and x y size 12{x cdot y} {} are algebraic expressions.

Expressions

Numerical expressions and algebraic expressions are often referred to simply as expressions .

Terms and factors

In algebra, it is extremely important to be able to distinguish between terms and factors.

Distinction between terms and factors

Terms are parts of sums and are therefore connected by + signs.
Factors are parts of products and are therefore separated by ⋅ signs.

While making the distinction between sums and products, we must re­member that subtraction and division are functions of these operations.
  1. In some expressions it will appear that terms are separated by minus signs. We must keep in mind that subtraction is addition of the opposite, that is,
    x y = x + ( y ) size 12{x - y=x+ \( - y \) } {}
  2. In some expressions it will appear that factors are separated by division signs. We must keep in mind that
    x y = x 1 1 y = x 1 y size 12{ { {x} over {y} } = { {x} over {1} } cdot { {1} over {y} } =x cdot { {1} over {y} } } {}

Sample set a

State the number of terms in each expression and name them.

x + 4 size 12{x+4} {} . In this expression, x and 4 are connected by a "+" sign. Therefore, they are terms. This expression consists of two terms.

y 8 size 12{y - 8} {} . The expression y 8 size 12{y - 8} {} can be expressed as y + ( 8 ) size 12{y+ \( - 8 \) } {} . We can now see that this expres­sion consists of the two terms y size 12{y} {} and 8 size 12{ - 8} {} .

Rather than rewriting the expression when a subtraction occurs, we can identify terms more quickly by associating the + or - sign with the individual quantity.

a + 7 b m size 12{a+7 - b - m} {} . Associating the sign with the individual quantities, we see that this expression consists of the four terms a size 12{a} {} , 7, b size 12{ - b} {} , m size 12{ - m} {} .

5 m 8 n size 12{5m - 8n} {} . This expression consists of the two terms, 5 m size 12{5m} {} and 8 n size 12{ - 8n} {} . Notice that the term 5 m size 12{5m} {} is composed of the two factors 5 and m size 12{m} {} . The term 8 n size 12{ - 8n} {} is composed of the two factors 8 size 12{ - 8} {} and n size 12{n} {} .

3 x size 12{3x} {} . This expression consists of one term. Notice that 3 x size 12{3x} {} can be expressed as 3 x + 0 size 12{3x+0} {} or 3 x 1 size 12{3x cdot 1} {} (indicating the connecting signs of arithmetic). Note that no operation sign is necessary for multiplication.

Practice set a

Specify the terms in each expression.

x + 7 size 12{x+7} {}

x , 7

3 m 6 n size 12{3m - 6n} {}

3 m 6 n size 12{3m - 6n} {}

5 y size 12{5y} {}

5 y size 12{5y} {}

a + 2 b c size 12{a+2b - c} {}

a , 2 b , c size 12{"a, 2b, "-c} {}

3 x 5 size 12{ - 3x - 5} {}

3 x , 5 size 12{-3x,-5} {}

Coefficients

We know that multiplication is a description of repeated addition. For example,
5 7 size 12{5 cdot 7} {} describes 7 + 7 + 7 + 7 + 7 size 12{7+7+7+7+7} {}

Suppose some quantity is represented by the letter x size 12{x} {} . The multiplication 5x size 12{5x} {} de­scribes x + x + x + x + x size 12{x+x+x+x+x} {} . It is now easy to see that 5 x size 12{5x} {} specifies 5 of the quantities represented by x size 12{x} {} . In the expression 5 x size 12{5x} {} , 5 is called the numerical coefficient , or more simply, the coefficient of x size 12{x} {} .

Questions & Answers

A golfer on a fairway is 70 m away from the green, which sits below the level of the fairway by 20 m. If the golfer hits the ball at an angle of 40° with an initial speed of 20 m/s, how close to the green does she come?
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Source:  OpenStax, Algebra i for the community college. OpenStax CNX. Dec 19, 2014 Download for free at http://legacy.cnx.org/content/col11598/1.3
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