lolly
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)
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surdawi
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y = mx + b
m=(y2-y1)/(x2-x1)
surdawi
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@lolly wanna try
lolly
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no..but i will..:)
Swageraid32
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(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
lolly
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can you set up the equation? then ill solve:P
surdawi
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(x1,y1) = (–1, –4)
(x2,y2) = (1, 4)
lolly
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soo y=mx=b? isnt that for finding slope?
surdawi
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yes but you need to find m 1st
\[y=\frac{ y2-y1 }{ x2-x1 }\]
surdawi
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meant m =
lolly
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ook ill try it..hold on..:)
lolly
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m=-6
lolly
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now what?
surdawi
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show me how?
surdawi
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m is wrong :D
lolly
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really?
lolly
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m= 1-4/-1--4.
m=-3/3
m=-6
surdawi
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(x1,y1) = (–1, –4)
(x2,y2) = (1, 4)
x1 = -1
y1 = -4
x2 = 1
y2 = 4
chrispearson813
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hi lolly :P
lolly
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right..thats what i did..,.i think..?
lolly
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hi..:)
03225186213
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(y-y1)/(y2-y1)=(x-x1)/(x2-x1)
lolly
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@surdawi how did i do it rong?
surdawi
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(4- - 4)/(1- -1)= 8/2=4
lolly
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so m is 4?
surdawi
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what you did (x2-y2)/(x1-y1)
lolly
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well i thought it was -6..but its not..?
surdawi
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m = 4
now you choose wither point and solve for b
y = 4x + b
lolly
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k hold on ill try again..:)
surdawi
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\[m=\frac{ y2-y1 }{ x2-x1 }=\frac{ 4- -4 }{ 1- -1 }=\frac{ 8 }{ 2 }=\]
03225186213
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for slope
slope=(y2-y1)/(x2-x1)
it can be directly solve see the formula that i have given already
03225186213
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(y-y1)/(y2-y1)=(x-x1)/(x2-x1)
lolly
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oooh!!! i got the x1and 2s switched up..ok i see..:)
surdawi
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|dw:1351797990809:dw|
lolly
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the one with less numbers right?
surdawi
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there is no zeros for x or y this time so pick one and solve, it doesnt matter which one
lolly
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which one would be easier?
surdawi
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either, same thing
lolly
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k ill do the one with less numbers..:P
lolly
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so 4=4x1=b? 4=b..but we already knew that..
surdawi
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both of them has same amount of numbers :p
4=4x1=b? !
why is there an equal to b
lolly
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oooh! whoop..my bad..:)
lolly
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so 4=4+4...
lolly
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4=8? that dosent make sense...
surdawi
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4=4x1+ b
what is x1 = ?
lolly
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-1
surdawi
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y1 =?
lolly
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-1
lolly
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000h!!!
lolly
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no it dosent..:)
lolly
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-4
surdawi
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it should be one of the pairs either (1,4) or (-1,-4)
-4 = 4*(-1) + b
lolly
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-4=4x-1=4?
surdawi
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4*-1=?
lolly
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-4
surdawi
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-4 = -4 + b
how can you keep b on one side?
lolly
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by adding 4 to b?
surdawi
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ok show me how?
lolly
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-4=-4+b (then the 4 crosses out)
+4 +4
surdawi
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-4 +4 = -4 + 4 +b
0 = b
y = 4x + 0
lolly
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where did the other set of -4=4 come from?
surdawi
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you have to add 4 to both sides
surdawi
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passes through points (–1, –4) and (1, 4)?
surdawi
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Anamaria what grade you in?
lolly
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10.:)
surdawi
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you should know how to add :P
lolly
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lol i do know how to add:)
lolly
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-4=-4+b (then the 4 crosses out)
+4 +4
was this rong?
lolly
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lol @surdawi u sleeping?
surdawi
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i went to pray
|dw:1351801108941:dw|
lolly
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lol were u praying that id understand how to do this? lol jk ook umm anyway i thought b=4?
surdawi
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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
lolly
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4 is not 8...? im so confused!!
surdawi
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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??
surdawi
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do you want me to give you problem to do?
surdawi
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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)
lolly
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noo i dont want another problem im too stuck with this one..:)
surdawi
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tell what you dont understand
|dw:1351802673845:dw|
lolly
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i dont really understand what you did..like at all... for the one on the right side...
surdawi
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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
lolly
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ok so b = 4 and 0?
surdawi
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no only 0
how do you get the 4?
lolly
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what we did earlier..
surdawi
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we never got b = 4
we got m is 4
lolly
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oooh!!!
surdawi
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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
lolly
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k thanks 4 ur help:)