How do you find the point of intersection for x+y= -3 and x+y=3?

1 Answer
MeneerNask
Jul 8, 2015

From x+y=3->y=-x+3=3-x

Explanation:

Now substitute that in the other equation:
x+y=x+(3-x)=-3->3=-3
This cannot be. Clearly there is no intersection.

We could have seen this, because (as we have seen before), the second equation translates to a slope-intercept form of
y=-x+3
While the first will translate to:
y=-x-3
Same slope (-1), but different intercepts (+3and-3), in other words, these are parallel lines.
Here is the graph for y=-x+3 the other one runs parallel and 6 units below it:
graph{-x+3 [-10, 10, -5, 5]}

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