Variables and Expressions #4

A variable is a letter or symbol that represents a quantity that can change. A constant is a quantity that does not change. Vocabulary

An algebraic expression contains one or more variables and may contain operation symbols. So p  7 is an algebraic expression. Algebraic Expressions NOT Algebraic Expressions y85 ÷ 5 35  w + z  5 To evaluate an algebraic expression, substitute a number for the variable and then find the value by simplifying. Vocabulary

Evaluate the expression to find the missing values in the table. Example 1: Evaluating Algebraic Expressions z z 

Example 2 Evaluate each expression to find the missing values in the table. t 8t

Evaluate each expression to find the missing values in the table. Example 3 m  m

Evaluate each expression to find the missing values in the table. Example 4 b 3  (2 + b) 3 6 9

You can write multiplication and division expressions without using the symbols  and . Instead of... You can write... x  3 x  3 35 ÷ y x(3) 3x3x 35 y When you are multiplying a number times a variable, the number is written first. Write “3x” not “x3.” Read 3x as “three x.” Writing Math

A rectangle is 4 units wide. How many square units does the rectangle cover if it is 3, 4, 5, or 6 units long? Example 5: Evaluating Expressions with Two Variables lwl x w

A rectangle is 7 units wide. What is the area of the rectangle if it is 8, 9, 10, or 11 units long? Example 6 7 · 8 = 56 square units;

A rectangle has a length of 13 units. The perimeter of a rectangle is twice its width plus twice its length. Complete the table to find the perimeter of the rectangle if its width is 5, 6, 7, or 8 units wide. Example 7 w l = 13