## manamesasher 3 years ago Solve the following system of equations graphically, find the graph 2x -y = -1 x + y = -2

1. manamesasher

2. manamesasher

3. manamesasher

2?

4. Calcmathlete

Easiest way to do this is to plug in the point of intersection and if both equations are true, then it's the correct answer. For instance, let's check 2. \[2x - y = -1\]\[2(1) - (-1) = -1\]\[2 + 1 = -1\]\[3 ≠ -1\]THerefore, it isn't 2.

5. manamesasher

i was talking about the graph...

6. Calcmathlete

Also, if the point of intersection is the same in two choices, then you have to make sure the lines make sense.

7. Calcmathlete

And yes, 2 is incorrect since the solution set is also the point of intersection when graphed...

8. manamesasher

9. Calcmathlete

Are you just guessing at this point?

10. manamesasher

no i'm asking if you can help me solve it...

11. Calcmathlete

Alright. I explained the process above... Let's take a look at choice 3... 2x - y = -1 Plus in the point of intersection, (-1, 1) 2(-1) - (1) = -1 -2 - 1 = -1 -3 ≠ -1 Do you see how the final equations ends up false since -3 does NOT equal -1?

12. manamesasher

ok. and choice 1, (-1, -1) 2(-1)-(-1)=-1

13. manamesasher

-1+-1=2

14. manamesasher

so it is choice 1..

15. manamesasher

thank you...

16. amistre64

my idea would be to use a knowledge of the equations to match the graph in this manner x + y = -2 notice this is pretty easy to turn to y = mx+b format y = -x-2 we need to find an option that has a line going thru y=-2 and a downill slope of -1

17. Calcmathlete

Um... \[2(-1) - (-1) = -1\]\[-2 + 1 = -1\]\[-1 = -1\]You should always check both equations by the way for the future, but it is indeed choice 1 :)

18. manamesasher

oh, ok sorry.. thanks again...

19. amistre64

1 and 3 fit the thru -2 part; and 3 is too steep for comfort

20. robtobey

A plot is attached.