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### Course: Algebra (all content)>Unit 1

Lesson 7: Dependent & independent variables

# Dependent & independent variables: equation

We're flipping the last video on its head and doing the opposite. This time we give you the graph and ask you to express it as an equation. Created by Sal Khan.

## Want to join the conversation?

• What is an independent and dependent variable. This is confusing me
• independent variable is x and dependent variable is y. the y-variable is dependent on the x-variable for its answer
• What does the t stand for and why do we have to put it in our answer
• T does not have to stand for anything, yet T stands for Time in months Sal says so at and we have to put it in the answer because otherwise we are just giving a number with no place where it goes.
• Can someone describe dependent and independent variables more clearly to me?

I think I get the gist, but if I stop thinking about it I forget.
• The dependent variable (most commonly y) depends on the independent variable (most commonly x). You can put in a value for the independent variable (input) to get out a value for the dependent variable (output), so the y= form of an equation is the most common way of expressing a independent/dependent relationship. In many real world situations, your logical part of brain will correctly identify the dependent variable (does ice cream sales depend on the weather, or does the weather depend on ice cream sales? does the dog running away depend on the gate being open, or does the gate being open depend on the dog running away?).
In real world equations particularly in Science, any of the variables can be dependent such as if v = d/t, then d = v t, and t = d/v, if two are given, I can solve for the third (velocity is distance divided by time).
• Independent because the distance from your home doesn't change
• In the name of this section it says it is inequalities, but this is not what I am doing in class, where do I find inequalities as in on a number line with the < and > symbols?
• Can a variable be another variable?
• A single quantity should be represented by only one variable, so you should not have two different variables used for the same thing. So if a question talks about finding Andy's age, you cannot use a and x both to represent the same thing. However, any variable can be named whatever you like so you can define a variable with any letter you want. You could also have two variables that are equal to each other such as y = x (linear parent function), but they are still two variables - one independent and one dependent, not just one variable which has a specific plot on a Cartesian plane.
If you are asking can you use other variables besides x and y to represent quantities, then yes you can define variables any way you want.
• I dont know how to do Algebra 1
• Does it have to be in a straight line?Also what does it mean if the line is not straight.
(1 vote)
• it doesnt really matter if the line is straight or not
(1 vote)
• what the difference between dependent and independent variable