Question 465060: y=-3x I am supposed to find the ordered pairs for this equation then graph them please explain the steps I am using course compass and it is telling me to substitute "-1" then "2" then "-2" into the equation for x. Is this true for all equations like this? I am confused because just last week he was saying that in order to find the pairs to substitute use zero confused...
Found 2 solutions by edjones, solver91311:
Answer by edjones(8007)   (Show Source):
You can put this solution on YOUR website! Make a table. Put x then y at the top and draw a long vertical line between. Put a zero below the x. What is y when x is 0? Ans: 0. Put a 0 in the y column (0, 0).
Put a one in the x column. What is y when x is 1. Ans: -3. put a -3 in the y column, (1, -3) an ordered pair. You can keep doing this for any value of (x,y).
Each ordered pair is a dot on a graph. Connect the dots to get a line.
.
Ed
Answer by solver91311(24713)  (Show Source):
You can put this solution on YOUR website!
A couple of facts to consider. The equation is linear, meaning the graph is a straight line. Recall from geometry that you only need 2 points to define a line. Also recall that any line consists of an infinite number of points. The instructions in "course compass" (whatever that is) that tell you to select three values to substitute for  is overkill -- you only absolutely have to have 2 points (However, remember that it is academically career limiting to ignore instructor or textbook instructions -- just sayin'). Furthermore, in any given situation, it doesn't matter what values you choose for , so long as you do the arithmetic correctly. Generally, it is easier to do the arithmetic if you choose small integers -- like the ones selected by your "compass" thing.
As for using zeros to replace the variables, that is a slightly different technique for graphing a straight line. This takes advantage of the characteristics of a couple of special points on a line in a Cartesian plane. The point where the line crosses (i.e. intersects or intercepts) the  -axis is called the -intercept and has the characteristic that the -coordinate of the ordered pair is equal to zero. The upshot is if you replace the in your equation with zero, then you will get some value for , let's call that value  and then the ordered pair for the -intercept is ) . Likewise, if you replace the in the equation with zero, you discover the value of the -coordinate of the -intercept, and the point is then ) . The problem with using this method on the problem you posed in this posting is that the graph goes through the origin, ) , which is to say that the and intercepts are the same point in this case. Since you need two distinct points to define a line, using the intercepts in this case won't work.
The thing to remember is that there is nothing sacred about any of the numbers anyone suggests as values to substitute. Do what is convenient for you and makes the arithmetic easier for you, unless you have specific instructions to do something differently. Capisce?
John
My calculator said it, I believe it, that settles it
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