SOLUTION: graph by first solving for y x-3y=9 x-9=3y divide both sides by 3 x-3=y or would it be y=1/3x Am I on the right track and how do you graph a fraction?

Algebra ->  Graphs -> SOLUTION: graph by first solving for y x-3y=9 x-9=3y divide both sides by 3 x-3=y or would it be y=1/3x Am I on the right track and how do you graph a fraction?      Log On


   



Question 110114: graph by first solving for y
x-3y=9

x-9=3y divide both sides by 3
x-3=y or would it be y=1/3x
Am I on the right track and how do you graph a fraction?

Found 2 solutions by Edwin McCravy, stanbon:
Answer by Edwin McCravy(20059) About Me  (Show Source):
You can put this solution on YOUR website!


graph by first solving for y    

   x - 3y = 9

get rid of the "x" term on the left by adding -x to both sides:

   x - 3y = 9
  -x          - x
---------------------
      -3y = 9 - x

Now divide every term by -3:

%28-3y%29%2F%28-3%29 = 9%2F%28-3%29 - x%2F%28-3%29

Simplify:

y = -3 + x%2F3

This is now solved for y. Next we have to 
get some points on the line.

Arbitrarily pick any convenient number to substitute
for x.  I think I will first choose 0 to substitute
for x.  I chose 0 simply because it is easy.  So we 
substitute x = 0

y = -3 + x%2F3
y = -3 + %28%280%29%29%2F3
y = -3 + 0
y = -3

So one point on the first line is (x, y) = (0,-3) 

Let's plot that point.  That point is on the
y-axis where y = -3

 

Now for the second point on the line, I think I will 
choose 3 to substitute for x.  I chose 3 simply because 
the term x%2F3 will be 3%2F3 or 1 so it
won't be a fraction.  I could have chosen any other 
number, but I can avoid fractions by choosing whole
numbers for x that are divisible by 3. So we substitute
x = 3

y = -3 + x%2F3
y = -3 + %28%283%29%29%2F3
y = -3 + 1
y = -2

So another point on the first line is (x, y) = (3, -2)

Now let's plot that point. It is directly below 3 on
the x axis and directly to the right of -2 on the
y axis:



We could draw a line through those two points.
However to be on the safe side, we should get
a third point. 

Now for the third point on the line, I think I will 
choose -6 to substitute for x.  I chose -6 simply because 
the term x%2F3 will be %28-6%29%2F3 or -2 so it
won't be a fraction.  I could have chosen any other 
number, but, as before, I can avoid fractions by choosing
whole numbers for x that are divisible by 3. So we 
substitute x = -6

y = -3 + x%2F3
y = -3 + %28%28-6%29%29%2F3
y = -3 + -2
y = -5

So another point on the first line is (x, y) = (-6, -5)

Now let's plot that point. It is directly below -6 on
the x axis and directly to the left of -5 on the
y axis:




Now we draw a straight line through all three
points.  



That's the graph of the equation

   x - 3y = 9

Edwin

Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
graph by first solving for y
x-3y=9
x-9=3y divide both sides by 3
x-3=y or would it be y=(1/3)x-1
----------------
Plot two points and draw a line thru them:
If x=0 y=-1
If x=3,y=0
----------
Plot the points (0,-1) (3,0)
----------------------
Graph:
graph%28400%2C300%2C-10%2C10%2C-10%2C10%2C%281%2F3%29x-1%29
==============
Cheers,
Stan H.