Answer:
Step-by-step explanation:
You need to know three things for this. First, the equation of a line inslope intercept form y=mx+b. m is the slope (rise over run) and b is the y intercept, or what happens when x equals 0. If either of these concepts are confsing let me know.
y=mx+b is going to be how we write the final answer, so we want to know how to fund m and b. b actually is found in the final step automatically, but m we have to use the points.
m is found with the equation (y2-y1)/(x2-x1). If this looks confusing it really isn't. (x1,y1) refer to one of the points you are givenand (x2,y2) refer to another. You are given points, but let's just try two of them and see if the third also fits. If it DOESN'T then we have to redo this or find another way, so keep that in mind. so, lets say (x1,y1) is (0,0) and (x2,y2) is (3,5). Remember, we could have made either one (-5,-25) or switched which we assigned. Also, it's worth noting if you ever have a point with one zero or especially two, that makes other parts easier.
Now the actual calculation.
(y2-y1)/(x2-x1)
(15-0)/(3-0)
I will leave simplifying for you. Remember, this is the slope, or m. Now, the third piece of the puzzle is what is called point slope form. This is what automatically gets you that y intercept. It's another case of plugging in numbers. y - y1 = m(x - x1). You are going to plug in m (the slope) and any of the three point's coordinates. You just have to make sure you plug inthe same y that goes with x. so if you plug -5 in for x1 you need to plug in -25 in for y1. Here's where (0,0) is super helpful. But I want you to try each of the points and see what happens.
After you plug it in you are going to want to solve for just plain old y. i will show you the calculation.
y - y1 = m(x - x1) First distribute the m
y - y1 = m*x - mx1 Then add y1 to both sides
y = mx - mx1 + y1
Now, we want y = mx + b. Well, if we have -mx1 + y1 equal to be then we have it, so we're done!
Again, you should try all three points in the last step just to see they make the same equation, and then use the final equation and plug in each x value to see if you get the same y value. It's all super valuable practice. And of course let me know if there's something you don't understand.
