Two distinct points A(x1, y1) and B(x2, y2) determine a line d, whose equation is:
The equation can be written as a determinant as follows:
If y2 = y1 and x2 ≠ x1 we have (d): y = y1
If y2 ≠ y1 and x2 = x1 we have (d): x = x1
The line's equation can be written like this:
, and if we write , where m is called slope of line we obtain this form
We can also determine the line's equation by cuts (i.e. where the line meets the Axis, in the points A(a, 0) and B(0, b)).
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