## Video transcription

How do you calculate the slope of a line? Hi, I'm Jimmy Chang. I've been teaching college mathematics for nine years. And when it comes to calculate slope, it kind of gives you an idea. as to what direction the line is going. It can be positive, negative, zero or even undefined. But here's a formula that's associated with slope. the letter that's used it always the letter m. And you need two points. An initial point and a terminal point. Now because initial point is the point of starting out with. It has ones as subscripts. So you have X1, Y1. And the terminal point because that's the point that you're ending with. Has twos as subscripts. So it's X2, Y2. Now the slope formula basically has you subtracting the Y coordinates on top and the X coordinates on the bottom. But if you notice, the twos, the coordinates representing the terminal point. Is the one mentioned first. Minus the initial. So it's the terminal coordinates minus the initial coordinates. Now what this gives you, is a ratio known as Rise over Run. Rise the vertical motion, run refers to the horizontal motion. So here's a case a case on point. Suppose you have two points. Two, three and seven, negative one. Now the two, three is your initial and seven negative one is your terminal. Basically, just pointing the formula like it's written and you'll be good to go. So you have Y2 which is negative one. Minus Y1 which is 3. Over X2 which is seven, minus the X1 which is two. So just do the subtraction. Negative one minus three is negative four. And seven minus two is equal to five. So the slope between these two points is negative four fifths. Now because you have a negative number for slope. That means it is a decreasing line. Which means the line is on a decline. So, my name is Jimmy Chang. And that's an example as to how you calculate slope.