Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2001/iii/paper-56/1/a/solution

The th coordinate plane has equation , hence covector . The line-plane incidence in Plücker coordinates formula reduces to
Thus the th column of the upper-index Plücker coordinates contains the intersection point's homogeneous coordinates, up to projective scaling. Its th entry vanishes as required. If that column is zero, both defining points have coordinate zero and the entire line is contained in the coordinate plane; there is no distinguished intersection point. Reading rows instead changes only the irrelevant overall sign.

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