tina-ann
solve the system of equations by graphing, f(x)=-1/2x +2 g(x)=9/2x -8
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3lroy
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ok
3lroy
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let me see
tina-ann
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someone please help me
3lroy
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but its pretty simple
tina-ann
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not for me i really suck at math, please help me step by step
dumbcow
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is this correct
f(x) = -(1/2)x + 2
f(x) = (9/2)x - 8
tina-ann
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not sure how to make the fraction symbols for -1/8 and 9/2
dumbcow
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thats ok me neither.
both of these are linear of the form y = mx+b
m = slope (rise/run)
b = y-intercept (where it crosses y-axis)
Now we need to graph each one
First identify y-intercept for our first point
1) b = 2
2) b = -8
put these points on the graph on the y-axis
dumbcow
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Next we look at slope to find second point
1) m = -1/2
This means starting at our y-intercept we go down 1 and over to right 2, repeat process for additional points
2) m=9/2
This means starting at y-intercept go up 9 and over to right 2
connect points to make each line
point where they intersect is the solution
tina-ann
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in the begining the first points b=2 b=-8 is that graphed as (2,-8)?
dumbcow
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oh sorry i meant 1) to mean line 1 and 2) to mean line 2
they are separate points
the x value is always zero for the y-intercept
(0,2) (0,-8)
tina-ann
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ok im really bad at this stuff
dumbcow
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when you think y-intercept, think y-axis....points will be directly on y-axis
tina-ann
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ok, so back to m=-1/2 and m=9/2
dumbcow
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yes start with the first one
go to starting point (0,2)
-1 means go down 1
2 means go right 2
plot a point
tina-ann
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ok so after i graphed them i came up with (2,1)?
dumbcow
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correct
this is the point where they cross
tina-ann
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ok do u have time to help me with more
dumbcow
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for a little bit, if nothing else i'll give you the steps
tina-ann
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ok f(x)=-1/8x-3 g(x)=5/8x-9
dumbcow
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same thing solve by graphing
dumbcow
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do the exact same steps we did before
the only thing that changes is the slope and y-intercept
dumbcow
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for f(x) = mx + b
m=-1/8
b=-3
dumbcow
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can you graph the first point from there
tina-ann
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start at 0 and go down the y to -3
dumbcow
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good
tina-ann
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same for (0,-8)
tina-ann
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they intercept at (2,-3) is that correct?
dumbcow
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careful the -8 was part of the slope for the first line
dumbcow
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the other y-intercept would be (0,-9)
tina-ann
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right , after i graphed them i got (2,-3)
dumbcow
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remember what the difference between m and b are
another way to think of it is the slope is always the number associated with the x, y-intercept is always the constant value
dumbcow
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no you should get (8,-4)
dumbcow
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starting at (0,-3)
go down 1
over right 8
tina-ann
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ok i got it
dumbcow
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ok good
keep repeating those steps
gotta go
good luck
tina-ann
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thank you so much
dumbcow
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your welcome
tina-ann
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thank you so much