## anonymous 5 years ago i need help solving this system by graphing??

1. anonymous

$\left\{ 2x+y=-7 \right\}$

2. amistre64

how do we graph in a text based area?

3. amistre64

the best we can do is set up a table of solutions

4. anonymous

$\left\{ -3x-2y=14 \right\}$

5. amistre64

substitution works pretty well in this scenario: can you solve the first equation for y?

6. anonymous

yes

7. anonymous

so, i subtract the 2y

8. amistre64

-2x yes

9. anonymous

ok

10. anonymous

so i get

11. amistre64

y = -7-2x; lets use this 'value' in the next equation

12. anonymous

y=-2x-7

13. amistre64

that ways good too ;)

14. anonymous

doesnt the -2x come before because it has an x

15. amistre64

it doesnt need to, but if you like it there; we can keep it there... it gets used up in the next one regardless

16. anonymous

ok

17. amistre64

-3x -2y = 14 - lets use that y value in this equation and solve for 'x'

18. anonymous

and for the other one i subtract the -3x

19. anonymous

To solve by graphing just means, draw the two lines and see where (if ever) they intersect.

20. amistre64

lets keep the other one as is and use out y value in it

21. amistre64

-3x -2y = 14 -3x -2(-2x-7) = 14 can you slove this ?

22. anonymous

yes\

23. amistre64

let me see you do it ;)

24. anonymous

ok

25. anonymous

ohh wait i dnt think i can solve this because it has two # before the paratheses

26. amistre64

-3x -2(-2x-7) = 14 -3x +4x +14 = 14 -3x +4x +14-14 = 14-14 -3x +4x +0 = 0 the two numbers are seperate terms, they dont interfere with each other

27. anonymous

oh ok

28. amistre64

-3x +4x = 0 it just takes a little bit to be able to 'see' the problem :) x = 0 this is our solution

29. anonymous

wait how did u get the x to = 0

30. amistre64

First step; plug in the value for y -3 -2(-2x-7)= 14 ; now distribute the -2 thru the paranthesis

31. amistre64

-3x +4x +14 = 14 do you see what i did there?

32. anonymous

you did distributive property

33. amistre64

yes, and since that was (-2) I used it in the process

34. amistre64

-3x +4x +14 = 14 ; now we subtract 14 from both sides -3x +4x +14-14 = 14-14

35. anonymous

and got 0

36. amistre64

correct; -3x +4x = 0 x = 0

37. anonymous

but dnt we have to get the values bythemselfs first

38. amistre64

by themselves? what are you refering to?

39. anonymous

like -3x-4x=0

40. anonymous

subtract then divide

41. amistre64

-3x+4x = 0 combine like terms -3x+4x = 1x right?

42. anonymous

yes

43. anonymous

then divide

44. amistre64

yes, we do divide by 1 if we need to :) then 1x = 0 ....x = 0

45. anonymous

oh ok

46. anonymous

in my multiple choices i do not have any one that has x=0

47. anonymous

48. anonymous

and y has 1 or -1

49. amistre64

we use 0 to find the value of y now and your choices are going to be (0,y)

50. anonymous

but there is no choice for that with 0.

51. amistre64

remember we found that y = -2x-7 right?

52. anonymous

yes

53. amistre64

unless you gave me the wrong equation information, this is what the answer needs to be :)

54. anonymous

no its all correct

55. amistre64

y = -2(0) - 7 y = -7

56. anonymous

its jst that they are on top of eachother .

57. amistre64

lets see if these answers work; -3(0)-2(-7)=14 0+14=14

58. anonymous

14=14

59. amistre64

2x+y = -7 2(0) + -7 = -7 0 +-7 = -7 -7=-7

60. anonymous

correct.

61. amistre64

so we have the correct solution; but what are your answer to choose from look like?

62. anonymous

(-4,-1) (4,1) (-4,1) (4,-1)

63. amistre64

....... then either those go to a different problem; or they are simply wrong :)

64. anonymous

i think they are wrong but idk.

65. amistre64

there can only be one solution to lines that cross; it is the point we found (0,-7)

66. anonymous

the problem is correct

67. anonymous

ok well thanks.:)

68. amistre64

if you ahve a teacher, bring it to their attention :)

69. anonymous

yes i will do that

70. amistre64

tag!!

71. anonymous

Stop that.

72. amistre64

lol tag

73. anonymous

Really really annoying.