What is Literal expression? — Mathematics

Definition 48.1 Primary & Middle School Mathematics · Chapter 48 — Literal Expressions

A literal expression is a computation containing one or more letters, each standing for a number. Writing conventions:

the sign $\times$ is dropped before a letter or a bracket: $3 \times a = 3a$ , $a \times b = ab$ , $2 \times (x + 5) = 2(x + 5)$ ;
but it stays between two numbers: $3 \times 5$ cannot be written $35$ !
$a \times a$ is written $a^2$ (“ $a$ squared”), $a \times a \times a = a^3$ ;
$1a$ is written $a$ , and $0a$ is $0$ .

Two formulas, valid for every rectangle: substitute the values of L and w to get numbers. — Two formulas, valid for every rectangle: substitute the values of $L$ and $w$ to get numbers.

Examples

Example 48.2

Simplify the writing:

5 \times x + 3 \times y = 5x + 3y, \qquad a \times 7 = 7a \ \text{(number first)}, \qquad x \times x \times 4 = 4x^2 .

Example 48.3 (Formulas are literal expressions)

For a rectangle of length $L$ and width $w$ : perimeter $P = 2(L + w)$ , area $A = Lw$ . One formula summarizes the infinitely many rectangles at once — that is the whole point of letters.

Read in context →