 This video is called Parallel, Perpendicular, or Neither, 2. What we're looking for is to see if these lines are parallel, perpendicular, or neither. So in example C, y equals 2x plus 1 and y equals negative 2x minus 1, it's important to remember that when talking about slope, you look at the number that's in front of the x or the number that's multiplying the x. So the first line has a slope of a positive 2. The second line has a slope of negative 2. Since the slopes are not the same, one is a positive 2, one is a negative 2, we know that they're not parallel. They're not opposite reciprocals either, so we would say the lines are neither parallel or perpendicular. They cross, but not at a 90 degree angle. The second example is a little bit different because they don't give us the lines in slope intercept form. They just tell us that the lines go through certain points. So line Km goes through point negative 5, negative 2, and m10, 7. So what we're going to have to do is calculate the slope of line Km and calculate the slope of line st. So when we look here, to calculate the slope of line Km, we're going to make a fraction and when you calculate slope, you subtract the y values on the numerator. So we will do 7 minus a negative 2 and then the denominator, we subtract the x values, 10 minus a negative 5. So on the top, the double negative becomes a positive. On the bottom, the double negative becomes a positive. So we have a slope of 9 over 15, which we could reduce down to 3 fifths. Now let's see what happens when we find the slope of line st. Oops, sorry. So again, we're going to subtract our y values. So I will do 4 minus 11 and 3 minus a negative 6. You add the opposite. We get a negative 7 and a positive 9. So you can see the slopes for Km and st, 3 over 5 and negative 7 over 9, they clearly aren't the same. They're not opposite reciprocals. So we would say these lines are not parallel or perpendicular. They will cross at some point, but just not at a 90 degree angle.