## lolly 2 years ago What is an equation for the line that passes through points (–1, –4) and (1, 4)? Write the equation in slope-intercept form. (2 points)

1. surdawi

y = mx + b m=(y2-y1)/(x2-x1)

2. surdawi

@lolly wanna try

3. lolly

no..but i will..:)

4. Swageraid32

(1,-4), m = -4 y = mx + b Sub to find b -4 = -4*1 + b b = 0 ------- y = -4x m = -4 means slope = -4. slope-intercept form of equation of a straight line is y = mx + b. m is the slope. b is the y-intercept. your equation starts of with the slope-intercept generic form of y = mx + b replace m with -4 to get y = -4x + b your line goes through the point (x,y) = (1,-4) that means the x-coordinate is 1 and the y coordinate is -4. to find the y-intercept, you replace y with -4 and x with 1 in the equation and solve for b. your equation of y = -4x + b becomes: -4 = (-4 * 1) + b

5. lolly

can you set up the equation? then ill solve:P

6. surdawi

@swiftskier96 is that the answer http://www.algebra.com/algebra/homework/Graphs/Graphs.faq.question.233716.html hahaha

7. surdawi

(x1,y1) = (–1, –4) (x2,y2) = (1, 4)

8. lolly

soo y=mx=b? isnt that for finding slope?

9. surdawi

yes but you need to find m 1st $y=\frac{ y2-y1 }{ x2-x1 }$

10. surdawi

meant m =

11. lolly

ook ill try it..hold on..:)

12. lolly

m=-6

13. lolly

now what?

14. surdawi

show me how?

15. surdawi

m is wrong :D

16. lolly

really?

17. lolly

m= 1-4/-1--4. m=-3/3 m=-6

18. surdawi

(x1,y1) = (–1, –4) (x2,y2) = (1, 4) x1 = -1 y1 = -4 x2 = 1 y2 = 4

19. chrispearson813

hi lolly :P

20. lolly

right..thats what i did..,.i think..?

21. lolly

hi..:)

22. 03225186213

(y-y1)/(y2-y1)=(x-x1)/(x2-x1)

23. lolly

@surdawi how did i do it rong?

24. surdawi

(4- - 4)/(1- -1)= 8/2=4

25. lolly

so m is 4?

26. surdawi

what you did (x2-y2)/(x1-y1)

27. lolly

well i thought it was -6..but its not..?

28. surdawi

m = 4 now you choose wither point and solve for b y = 4x + b

29. lolly

k hold on ill try again..:)

30. surdawi

$m=\frac{ y2-y1 }{ x2-x1 }=\frac{ 4- -4 }{ 1- -1 }=\frac{ 8 }{ 2 }=$

31. 03225186213

for slope slope=(y2-y1)/(x2-x1) it can be directly solve see the formula that i have given already

32. 03225186213

(y-y1)/(y2-y1)=(x-x1)/(x2-x1)

33. lolly

oooh!!! i got the x1and 2s switched up..ok i see..:)

34. surdawi

|dw:1351797990809:dw|

35. lolly

the one with less numbers right?

36. surdawi

there is no zeros for x or y this time so pick one and solve, it doesnt matter which one

37. lolly

which one would be easier?

38. surdawi

either, same thing

39. lolly

k ill do the one with less numbers..:P

40. lolly

so 4=4x1=b? 4=b..but we already knew that..

41. surdawi

both of them has same amount of numbers :p 4=4x1=b? ! why is there an equal to b

42. lolly

43. lolly

so 4=4+4...

44. lolly

4=8? that dosent make sense...

45. surdawi

4=4x1+ b what is x1 = ?

46. lolly

-1

47. surdawi

y1 =?

48. lolly

-1

49. lolly

000h!!!

50. lolly

no it dosent..:)

51. lolly

-4

52. surdawi

it should be one of the pairs either (1,4) or (-1,-4) -4 = 4*(-1) + b

53. lolly

-4=4x-1=4?

54. surdawi

4*-1=?

55. lolly

-4

56. surdawi

-4 = -4 + b how can you keep b on one side?

57. lolly

58. surdawi

ok show me how?

59. lolly

-4=-4+b (then the 4 crosses out) +4 +4

60. surdawi

-4 +4 = -4 + 4 +b 0 = b y = 4x + 0

61. lolly

where did the other set of -4=4 come from?

62. surdawi

you have to add 4 to both sides

63. surdawi

passes through points (–1, –4) and (1, 4)?

64. surdawi

65. lolly

10.:)

66. surdawi

you should know how to add :P

67. lolly

lol i do know how to add:)

68. lolly

69. lolly

lol @surdawi u sleeping?

70. surdawi

i went to pray |dw:1351801108941:dw|

71. lolly

lol were u praying that id understand how to do this? lol jk ook umm anyway i thought b=4?

72. surdawi

lol muslims pray 5 times a day not only sundays :P ok plug in b = 4 to check y = 4*x + 4 (1, 4) 4 = 4*1 + 4 4 = 8? is that right

73. lolly

4 is not 8...? im so confused!!

74. surdawi

thats would be the answer if b was 4 correct answer is y = 4x + 0 = 4x plug in and check and where is my medal at??

75. surdawi

do you want me to give you problem to do?

76. surdawi

try solving this What is an equation for the line that passes through points (2,5) and (6,7)? Write the equation in slope-intercept form. (you pay \$10 hehe)

77. lolly

noo i dont want another problem im too stuck with this one..:)

78. surdawi

tell what you dont understand |dw:1351802673845:dw|

79. lolly

i dont really understand what you did..like at all... for the one on the right side...

80. surdawi

ok (-1,-4) now we need to substitute that into y =mx + b y = -4 x = -1 m = 4 y = m* x + b -4 = 4*(-1) + b -4 = -4 + b we now need to add a 4 to both sides -4 = -4 + b +4 +4 -------------- 0 = 0 + b ===> b = 0

81. lolly

ok so b = 4 and 0?

82. surdawi

no only 0 how do you get the 4?

83. lolly

what we did earlier..

84. surdawi

we never got b = 4 we got m is 4

85. lolly

oooh!!!

86. surdawi

i have to go to my Advance Engineering Math :( right now; which doesnt look like anything on here...try to figure it out; if you still have problems feel free to message me the answer is y = 4x

87. lolly

k thanks 4 ur help:)