slope intercept form

[elowah]

My son is having trouble with this. He has a large chapter est coming up and we are trying o figure out where he is going wrong. Here are 2 equations he got wrong on quiz:
The instructions are Solve for y, state m and b, and graph.
the 2 problems are: (and I will show the work he did)
5x - y = 7
-5x -5x
-y= -5x + 7
-1 -1 -1
y = + 5/1x + 6
b= 6
m=5



x - 3y + 6 = 0
-x -x
3y + 6 = -x
-6 -6
-3y/-3 = x-6/-3
y = 3x + 2
b=2 m=3

Ok I hope you all can understand what I typed. It has been 22 yrs since I had algebra and am trying to figure out the steps(in plain english) how to do these. Any help would be greatly appreciated!

 

[Deleted member 4993]

My son is having trouble with this. He has a large chapter est coming up and we are trying o figure out where he is going wrong. Here are 2 equations he got wrong on quiz:
The instructions are Solve for y, state m and b, and graph.
the 2 problems are: (and I will show the work he did)
5x - y = 7
-5x -5x
-y= -5x + 7
-1 -1 -1
y = + 5/1x + 6 <<< Why is that ?- you are multiplying by "-1" not adding here.
b= 6 <<< That should be -7
m=5



x - 3y + 6 = 0
-x -x
3y + 6 = -x <<< missed "-" in front of "y"
-6 -6
-3y/-3 = x-6/-3
y = 3x + 2 <<< here you are dividing by "-3" - not multiplying
b=2 m=3 <<<< This should be 1/3

Ok I hope you all can understand what I typed. It has been 22 yrs since I had algebra and am trying to figure out the steps(in plain english) how to do these. Any help would be greatly appreciated!

 

[mmm4444bot]

5x - y = 7
-5x -5x

-y= -5x + 7
-1 -1 -1 (I guess this means multiply each term by -1 ?)

y = + 5/1x + 6 (Write 5x, not +5/1x.)

Seven times negative one is not six !

b= 6
m=5 This slope is correct.



x - 3y + 6 = 0
-x -x

3y + 6 = -x He forgot to write -3y.
-6 -6

Where is the result after subtracting six from both sides?

-3y/-3 = x-6/-3 Again, he forgot to write -x.

y = 3x + 2 -x/(-3) is not 3x !

b=2 This y-intercept is correct.

m=3

Your son's problem seems to be very sloppy arithmetic.

It's important to keep track of negative signs.

It's important to keep track of what you're doing. (If you begin multiplying terms by -1, then don't switch to addition midstream !)

5x - y = 7

Since we want to end up with a positive y, we can begin by adding y to both sides.

5x = y + 7

Subtract seven from both sides to finish.

y = 5x - 7

----------------

x - 3y + 6 = 0

Since we want to end up with a positive y, we can begin by adding 3y to both sides.

x + 6 = 3y

Divide both sides by 3 to finish.

x/3 + 6/3 = 3y/3

x/3 + 2 = y

Write the slope as a number multiplied by x (i.e., a coefficient).

y = (1/3)x + 2

Now the value of m is clear.

 

[elowah]

thanks! I see where he went wrong. I am not up to par on my algebra anymore so when I look at his work I do miss some basic facts that he has wrong. So it seems he has the general idea but needs some work on the steps to get there.