Solution

ID: past-exam-of-the-mathematics-course-of-the-year-1-of-the-natural-sciences-course-of-the-university-of-cambridge/2023/paper-2/11/c/i/solution

Use displacements from , since coplanarity of points concerns an affine plane that need not contain the origin. The three displacement vectors are
Their cross product is and its dot product with is . Since the scalar triple product is nonzero,
The four points do not lie in a common plane.

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