Posted by Jaison on Wednesday, October 28, 2009 at 3:47pm.
solve by graphing:
x+y=1
2x+y=0
I know that the answer is (1,2)and i know how to mark the spot but can you explain how to draw the lines because i cant figure out the directions it goes in.

Math  jim, Wednesday, October 28, 2009 at 4:55pm
To graphing a straight line:
1. Draw your axes.
2. Set x=0 in your equation to get the yintercept:
x + y = 1
0 + y = 1
y = 1
so we have one point: (0,1)
3. Set y=0 in your equation to get the xintercept:
x + y = 1
x + 0 = 1
x = 1
so we have a second point: (1.0)
4. Mark the two points on your graph, and use a ruler to draw the straight line that goes through them.
I usually go for the x and yintercepts as my points, but any two points will do. Sometimes you can't use two intercepts, as in your second equation:
2x + y = 0
2(0) + y = 0
y = 0
So the origin (0.0) is on this line.
The x and yintercepts are the same.
We need another point. No problem; just set x = anything else, for example 3:
2x + y = 0
2*3 + y = 0
y = 6
So we can use the point (3, 6) as our second point. Mark it, and get out the ruler again to draw a straight line through (3, 6) and the origin.
The two lines should meet at the point you expect.
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