You don't have to use any particular form of the equation.
In fact, this problem asks you to graph the lines, and solve the system of equations using the graphs.
For example,
http://www.wolframalpha.com/input/?i=plot+6x+-+3y+%3D+24+%2C+18x+%2B+3y+%3D+12+
Using a graph, solve for x and y below.
If 6x - 3y = 24
&
18x + 3y = 12
I know to use the forumla y = m*x + b. I also know to assume x=0 so that your starting point is (0,b) with b representing the y axis. M represents slope, which is rise over run. What I am having trouble with is working one of the equations so it fits the formula in. Any help or insight would be greatly appreciated. Thanks!
3 answers
My apologies. I guess I didn't word my question properly. The instructor needs us to show our work, so I have to show how I get the starting points on the graph.
Here is what I have so far. Maybe you can see where I am going wrong.
18x+3y=12
3y=18x+12
y=-18x+4
This gives me starting points of (0,4)
6x-3y=24
-3y=-6x+24
-y=2x-8
y=-2x+8
This gives me starting points of (0,8)
For the first equation, I would use the starting point, then go down 18 and to the right 1. Same for the second: down 2, 1 to the right.
That doesn't match the graph you linked to, and I can't seem to figure out where the mistake is being made.
Here is what I have so far. Maybe you can see where I am going wrong.
18x+3y=12
3y=18x+12
y=-18x+4
This gives me starting points of (0,4)
6x-3y=24
-3y=-6x+24
-y=2x-8
y=-2x+8
This gives me starting points of (0,8)
For the first equation, I would use the starting point, then go down 18 and to the right 1. Same for the second: down 2, 1 to the right.
That doesn't match the graph you linked to, and I can't seem to figure out where the mistake is being made.
each graph is a line. You don't need to use y=mx+b to "start."
18x+3y=12
or,
6x+y=12
If x=0, y=12
if y=0, x=2
So, plot the points (0,12) and (2,0) and join them in a line.
Using the Ax+By=C (standard) form is very convenient, since you can easily get both intercepts just by making one of the variables zero.
For the first one, if you go down 18 and to the right 1, you are plotting a line with slope -18. But the slope is really -6. You did not divide the 18 by 3, as you did the other terms.
18x+3y=12
or,
6x+y=12
If x=0, y=12
if y=0, x=2
So, plot the points (0,12) and (2,0) and join them in a line.
Using the Ax+By=C (standard) form is very convenient, since you can easily get both intercepts just by making one of the variables zero.
For the first one, if you go down 18 and to the right 1, you are plotting a line with slope -18. But the slope is really -6. You did not divide the 18 by 3, as you did the other terms.
0 answers