If I'm not mistaken, the first equation in this problem represents a line, not a plane. Do I leave it blank? There's no option that describes a line.
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Well, what you say would be true in the right situation, except that you've mistaken the situation. Notice that clause about "equations represent in R^3"? So if you need three variables needed to describe points in R^3, say x, y, z, and you've got a single equation that contains only two of those variables, does that equation constrain the value of the third variable at all?
