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.

Lesson 4: Slope

# Slope (more examples)

Given two points on a line, you can find the slope of the line. Watch Sal doing a bunch of examples. Created by Sal Khan and CK-12 Foundation.

## Want to join the conversation?

• What language does the word "Delta" originate.
• Delta is the fourth letter of the greek alphabet. ex. Alpha, beta, gamma, DELTA right there.
• At in the video, Khan says a vertical slope would be undefined. Why is that?
• Although "undefined" is technically correct, it is practically unsatisfying.
• Rate of change is also used to describe the second derivative of a function, can you make a video that explains how this works exactly? If I remember correctly you should be able to use that to determine if a point f'(x) = 0 is a Maximum point of Minimum point.. I'm just not quite sure how and why..
• @ Oskar. Please take a look at the Calculus videos. Your question is advanced for this section. To answer your question, the 2nd derivative is actually the rate of change of the rate of change. You can use both a 1st derivative and the 2nd derivative test to determine local maxima and mininma.
If f '(p) = 0 and f "(p)>0 then f has a local minimum at p.
If f '(p) = 0 and f "(p)<0 then f has a local maximum at p.
• At , Sal says the slope is undefined. Can't he just say there is no slope or is that something else?
• zero is horizontal undifined is vertical
(1 vote)
• At , why does he put y/x? Would it also work the other way round?
• Nope the other way will mess you up in a very bad way
(1 vote)
• At , Sal explains that slope is the change in y with the with in x. What is the triangle doing next to each of the variables?
• The triangle is the "Delta" the fourth letter in the Greek alphabet.Delta means change in.
(1 vote)
• Does the slope of the line depend on the start and end points,
because in the second example(at ) there are two slopes : one negative and one positive , so in the negative slope if we took the starting point as (5,-6) then the slope would be positive, right? So my question is, can we take any point as a starting point or only a specific point?
• The slope of a line is constant. You can pick any 2 points and calculate the slope. If your math is correct, then you get the same result.
• How do you decide which point is the start and which point is the finish?
• It doesn't matter. You can pick any 2 points to calculate the slope of a line. And, it doesn't matter which one you start with.
• so basically just go to the side and up right