Where is this x term? It's completely gone. We're looking for y is equal to mx plus b. Splitting the second and fourth quadrants. When you move to the right byġ, when change in x is 1, change in y is negative 1. Where's the b term? I don't see any b term. If you go backwards, if you moveĥ backwards- instead of this, if you view thisĪs 1 over negative 5. The delta y over delta x isĮqual to negative 1/5. ![]() This tells us that for everyĥ we move to the right, we move down 1. I can't draw lines too neatly, but this is going X-direction, I move down 2 in the y-direction. X-direction, I move up 2 in the y-direction. That's the y-interceptĪnd the slope is 2. So when x is equal to 0, y isĮqual to one, two, three, four, five. Y-intercept- that's the m, that's the b- and actually Lines knowing that this is the slope and this is the So the equation here is y isĮqual to 1/2 x, that's our slope, minus 2. What is our change in y? Our change in y is positive 2. And then what is the slope? m is equal to change inīy one, two, three, four. Here the equation is y isĮqual to 3x plus 1. What is our y-intercept? Well, when x is equal toĠ, y is equal to 1. We go to the right, our change in x is 1. Right, what happens to our delta y? We go up by 3. So we'll know that the equationī, plus 4/3. So this right here mustīe the point 1 1/3. You can't exactly see it there,īut you definitely see it when you go over by 3. When our change in x is 3, ourĬhange in y is negative 2. Y is equal to- we go down by 2- it's equal It because I want to hit an even number here- our delta So what is A's slope? Let's start at someĪrbitrary point. So we're going to look at these,įigure out the slopes, figure out the y-intercepts and Now given that, what I want toĭo in this exercise is look at these graphs and then use theĪlready drawn graphs to figure out the equation. To be the slope and this is definitely going to be So hopefully you're satisfiedĪnd hopefully I didn't confuse you by stating it in theĪbstract with all of these variables here. ![]() Point, so you have m plus b, our change in y, m plus b minusī over our change in x, over 1 minus 0. That point and that point? Let's take this as the end Is really the slope, let's just try some numbers out. We'll see that withĪctual numbers in the next few videos. If x is equal to 0, thisĮquation becomes y is equal to m times 0 plus b. Remember x is equal to 0, that means that's where we're going Where m is the slopeīeen dealing with the last few videos. Know that any linear equation can be written in the form ![]() Now we can just put everything in our slope-intercept equation: Ta-da! b, our y-intercept, is equal to 4/3. Then find a point on the line-literally any point with whole coordinates will do. We already known what m is = -2/3 (the slope.) We now have y = (-2/3)x + b. This is my strategy:įirst take a look at the slope-intercept form: y = mx + b. But sometimes it's not so clear as to where the point is. Look at the point where the line intersects the y axis, or the axis going in the vertical direction. He chooses the coordinates (-1, 2) and (2, 0). ![]() Or, you can physically draw the lines and count the units like Sal does in the video. Then use the following expression to find the slope: (y2-y1)/(x2-x1). Find two points on the line that have clean, whole numbers as coordinates. Remember that slope is rise/run, or change in y over change in x. When you try to write a slope-intercept equation from a graph, there are three steps you need to take:
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