Question about Computers & Internet
It depends on how complex the function is; there are different techniques. For a straight line of the standard form, usually shown as y=mx+b; this is a simple function of y in terms of x. So, determining the function in this case means finding values for m and b. --- m is the slope of the line, commonly called rise over run. Since your question asks in terms of coordinates, I would assume that you are looking at a problem giving you 2 points.
Probably something like p1 = (3,4); p2 = (5,8); the general form of this is p1=(x1,y1); p2=(x2,y2). The slope in this case is rise over run, in other words, the change in y divided by the change in x. This can be calculate between these two points as (y2-y1)/(x2-x1). In my sample above, this would be (8-4)/(5-3) = 4/2 = 2 giving the value of m.
To find the value of b (the y intercept) you need the value of y when x = 0. Since you already know that m, the slope is 2, consider a new point, call it p3 (x3,y3), pick either of the known points and solve the slope equation again, this time for y3. [m=(y3-y1)/(x3-x1)]. We know that x3 is 0, since we are trying to solve for y where that is true, so the equation becomes:
y3 is really b in the standard form, since it is, by definition the intercept, or the value when x=0,
b=y1-x1*m -- this gives you the y intercept anytime you know the slope and one point on the line.
In the example, y1 = 4, x1=3 and we've already calculated m to be 2, so
b=4-3*2 = -2
So, the function would be
y = 2x -2
To check, plug in the values of the other point, p2, and see if they work
y2 = 2*x2 - 2
It's easier than it looks. It can help you to understand if you get some old fashioned graph paper and plot it so you can see what is happening.
Posted on Jun 18, 2009
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Posted on Jan 02, 2017
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