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IMO 1967 - Longlist Problems Question 33

IMO Shortlist · IMO 1967 - Longlist Problems

Question 33

(MON 4) In what case does the system
$$\begin{aligned}x+y+mz&=a,\\x+my+z&=b,\\mx+y+z&=c\end{aligned}$$
have a solution? Find the conditions under which the unique solution of the above system is an arithmetic progression.