Question

Solve the system of equations by graphing. Then classify the system. x + y = 9 and x - y = 5. What is the ordered pair (if any)? Is the system consistent or inconsistent? Are the equations dependent or independent?

Answer 1

The ordered pair is (7, 2). I am not sure how to plot that on the graph.

Answer 2

Or how to determine if it is inconsistent or consistent, dependent or independent.

Answer 3

Definition 6.1 A system is consistent if there is at least one solution.

Definition 6.2 A system is underdetermined when there are an infinite number of solutions.

Answer 4

good, solution is (7,2)
go to graph, start at origin, go 7 to the right, then up 2, plot a point.

The only time a system is inconsistent is if there is No solution.
The only time equations are dependent is if there are infinite number of solutions

Answer 5

gotta right that down, that is a good way to remember.

Answer 6

now, when I go over 7 to the right and then up 2, how do I get the line to stop following me? Can I go straight down (or up) and plot my point at the end of the graph?

Answer 7

This would make a straight line.

Answer 8

not sure what you mean
you are not drawing a line just drawing a point which represent where the 2 lines cross

Answer 9

I am not sure how to just plot a "point." It creates a line and when you try to move the cursor, the line moves with you. Hard to explain.

Answer 10

oh this is a online graph, yeah i think you click 2 points and it automatically creates the line for you
i dont know, does it ask you to plot the point or draw the 2 lines ?

Answer 11

Yes, this is an online graph. If I go over 7 then up 2 it makes a vertical line. I have no second line to plot, that is what is confusing me.

Answer 12

don't click on (7,0) , i think its making a vertical line because you are clicking on 2 points
only click on (7,2) what i mean is go over 7 but dont click then up 2 then click :)

Answer 13

That is what I am trying to do, but when I try to move from that point, the line moves with my cursor. I can't figure out how to make the plotted point "stick"

Answer 14

hmm i dunno, look at graph options, maybe you are in line mode or something

Answer 15

okay, I'll check it out. Thanks for helping me.

Answer 16

no problem

Answer 17

could it perhaps be make like a x kind of thing. So if you go to 7 and click once it makes a line there and switches to a horizontal line at 2

Answer 18

I think so, let me check

Answer 19

Yes, but the horizontal line is like a ghost line when I hold the cursor up 2 but when I click it, the horizontal line goes away. I do think it is supposed to resemble an "x" but I just can't seem to make it do what I want.