If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

## Algebra 1

### Unit 14: Lesson 1

Intro to parabolas

We can interpret what the features of a graph of a quadratic model mean in terms of a given context. Created by Sal Khan.

## Want to join the conversation?

• Why is a quadratic equation called "quadratic"? The prefix "quad-" means four, but a quadratic equation only has a degree of two. Is there something else behind it? • I have wondered why “4” was used for a “2”. It didn't seem to make any sense at first. However, in Latin:
• Linear means a line, and having 1 dimension contains 1 solution
• Quad refers to a square, which has 2 dimensions and thus has 2 solutions
• Cubic refers to a cube, which has 3 dimensions and thus has 3 solutions
So it seems that the "quad" is focusing on the number of sides the shape has (while not yet about the number of solutions); it means a "square-like" equation. This is why the “2nd-power” is called “squared”, because for whatever value is “squared” the result produces the shape of a square. A square has 4 sides, and this is likely what “quad” or “four” is coming from.
• Do you solve these any different if they have endpoints instead of continued lines? 