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MathNet 2017-part-07 — 172 problems (EN–VI) Question 152

Math Olympiad Vault · MathNet 2017-part-07 — 172 problems (EN–VI)

Question 152

Two ordered pairs $(a, b)$ and $(c, d)$, where $a, b, c, d$ are real numbers, form a basis of the coordinate plane if $a d \neq b c$. Determine the number of ordered quadruples $(a, b, c, d)$ of integers between $1$ and $3$ inclusive for which $(a, b)$ and $(c, d)$ form a basis for the coordinate plane.