Variable Expressions

Key Questions

  • What are variable expressions?

    Variable expressions are expressions that involve variables, which are symbols that represent changing quantities. (See http://socratic.org/questions/what-are-variables for reference). The value of the expression will change as the value of the variable changes.

    For example, let's say with have the equation x + 5

    When x = 1 , then x + 5 = 6

    When x = 2 then x+5 = 7

    Hope that was helpful.

    Kevin B. · 1 · Mar 19 2015
  • How do you write variable expressions?

    To write variable expressions on Socratic, simply place hash tags around the expression when typing it:

    [hash tag] x + 1 [hash tag] = x +1

    [hash tag] (x-1)/(x+1) [hash tag] = (x-1)/(x+1)

    Hope that was helpful.

    Kevin B. · 1 · Mar 19 2015
  • How do you evaluate variable expressions?

    To evaluate a variable expression means to find the value of the expression when the variable is (or variables are) replaced by a number (or numbers).

    Here is a variable expression: 3x+7.

    To evaluate this expression when x = 2 mean to substitute 2 in place of x, and find the number (the value). [see note below]

    3(2)+7 = 6+7 = 13.

    When x=2, the expression has a value of `13.

    If we evaluate the same expression when x=10, we get:

    3(10)+7 = 30+7 =37.

    Here's a variable expression with two variables : 3x-2y

    In order to evaluate this expression, we'll need values (numbers) for both x and y.

    Evaluate the expression 3x-2y when x=4 and y=5

    3(4)-2(5) = 12 - 10 = 2

    If we change the values to x=5 and y=4, we get
    3(5)-2(4) = 15 - 8 =7.

    Note:

    To avoid saying exactly the same thing over and over, we use the following to mean the same thing:

    evaluate the expression when x = 2
    evaluate the expression for x = 2
    evaluate the expression at x = 2
    evaluate the expression assuming x = 2
    evaluate the expression if x = 2

    Also

    If there is only one variable in an expression, we don't always need to mention it:
    evaluate the expression for 2
    evaluate the expression at 2

    Jim H · 1 · Apr 26 2015
  • What are variables?

    Variables are symbols representing some changing quantities.

    I hope that this was helpful.

    Wataru · 3 · Nov 11 2014

Questions

Expressions, Equations, and Functions