## BrizyBaby16 3 years ago What quadrant are the equations in? A. 3x + 2y = -15 x - 4y = -20 B. 10x - y = -30 x - y = -2 C. 2x - 5y = 10 x + 2y = 10 D. 3x + y = 9 -7x - 7y = -14

1. aminah.love18
2. aminah.love18

go there for some accuarate help

3. BrizyBaby16

I don't have a library card #. That's not going to help me.

4. aminah.love18

240100447204

5. aminah.love18

try that

6. aminah.love18

lemme know what happens

7. BrizyBaby16

It worked but I don't see it helping me too much.

8. aminah.love18

ok you shouldve pressed the math section

9. BrizyBaby16

I did.

10. aminah.love18

ok then you fill out the information on the bottom it shouldve let you type in your qestion

11. BrizyBaby16

Would this be algebra I or II?

12. aminah.love18

algebra 2

13. BrizyBaby16

What subtopic?

14. aminah.love18

15. BrizyBaby16

would it be graphing functions?

16. aminah.love18

yes

17. BrizyBaby16

I just need to know how to graph them.

18. aminah.love18

girl go the bottom of tha page and get a tutor a live tutor will help you out

19. BrizyBaby16

I don't like that site.

20. aminah.love18

lol ok then well their helpful i jsut uesd them rite now and they gave me the rite answer to everyting

21. keketsu

Brizy, here's something else you can also try. Go to http://fooplot.com. It will graph the equations for you and you can see what quadrants they are in. You do have to solve for y first. So your first equation in A would be: 3x + 2y = -15 2y = -3x - 15 y = (-3/2)x - (15/2) Then you'd enter everything right of the "=" sign on that website. Hope that helps.

22. aminah.love18

now thats coool im gonna try that

23. BrizyBaby16

Yeah that seems complicated :-(

24. aminah.love18

my god girl you are hard to please

25. BrizyBaby16

Lol I've herd that before :-)

26. keketsu

Haha. It does take some work, but that process should at least make it easier.

27. aminah.love18

ya try it

28. aminah.love18

Still is.

30. aminah.love18

aaaaahhhhhh

31. aminah.love18

have i metntioned you look wonderful today:)

BrizyBaby—the easiest way to answer these question is usually to graph them, honestly.

33. BrizyBaby16

I don't know how to graph the equations....that's what I need help with.

Got it! Now we're at the heart of the problem :)

Let's start with A then. We have two equations: 3x + 2y = -15 x - 4y = -20

36. aminah.love18

well i give up nice meeting you thoug Brizzy

37. BrizyBaby16

I need a easy way to know how to graph them.

38. BrizyBaby16

You too aminah.love18

I find it easiest to graph equations when they're in y = mx + b (slope-intercept) form. So first things first, we try to solve the equations for y: \begin{align} 3x + 2y &= -15\\ 2y &= -3x - 15\\ y &= \frac{-3x - 15}{2} = -\frac{3}{2}x - \frac{15}{2} \end{align} And the other one: \begin{align} x - 4y &= -20\\ -4y &= -20 - x\\ y &= \frac{-20 - x}{4} = \frac{-20}{4} - \frac{1}{4}x\\ y &= -5 - \frac{1}{4}x = -\frac{1}{4}x - 5 \end{align}

So, we now have: y = -3/2 x - 15/2 y = -1/4x - 5 The first thing to notice is that both of these have a negative slope. Do you know what a negative slope means on a graph?

41. BrizyBaby16

I don't get how you did the equations but yeah a negative slope goes down left to right.

Whoops. Sorry then, let's go back to that :) Let's start with 3x + 2y = -15. We're trying to solve for y. That means we need y alone. Remember that an equation doesn't change if we subtract the same thing from both sides. So first things first, we move the 3x to the right: 3x + 2y = -15 3x - 3x + 2y = -15 - 3x Subtract 3x from both sides, 3x - 3x is 0: 0 + 2y = -15 - 3x 2y = -15 - 3x (We leave off the 0.) Then we need to get rid of the 2. Dividing the same thing from both sides also leaves the equation unchanged, so we'll divide by 2: y = (-15 - 3x) / 2 y = -15/2 - 3/2 x Does that make more sense?

43. BrizyBaby16

yeah. So the points are -7.5 and -1.5?

Close! :) This means that the line is, like we said, going top left to bottom right. It means for every 3 units down that it goes, it goes two units to the right. And it means that it meets the y axis at -7.5. A quick, semi-accurate drawing: |dw:1329863330467:dw|

45. BrizyBaby16

What did I get wrong?

So you can see here that that line is in quadrants II, III, and IV: |dw:1329863470553:dw|

-1.5 isn't a point, it's the slope, that's all.

48. BrizyBaby16

So, it's in the third Quadrant?

Well, that's what I'm not 100% clear on in the question. Obviously this line goes through three quadrants. Is the question asking which quadrant both lines are in or..?

50. BrizyBaby16

Well does it mean what quadrant the slope is in?

Sorry -> slope isn't really in a quadrant. It just tells you how the line moves from one position to another (i.e., what angle it's at).

It probably means what quadrant the two lines meet in, so let's look at the other line.

y = -1/4x - 5 So we have a slope of 1/4, meaning for every one unit we go down, we move to the right 4 units. And -5 is the y-intercept, which means the line meets the y axis at -5. Another rough drawing: |dw:1329864223848:dw|

If we put the two together: |dw:1329864317169:dw|

You can see there that they do in fact intersect in quadrant III.

56. BrizyBaby16

So for A it's Quadrant III?

I would assume so. Again, the question isn't *super* clear, but I think that's what it's asking for.

58. BrizyBaby16

Okay thanks :-)