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Difficulty: 4/102024 IOQM 2024 (Q10)

Determine the number of positive integral value of for which there exists triangle with side a, and which satisfy a2 + (p2 + 9)b2 + 9c2 – 6ab – 6pbc = 0

Guide / Hint

Hint 1: Start by analyzing the initial conditions and setting up the basic equations. a2 + 9b2 – 6ab + p2b2 – 6pbc + 9c2 = 0.

Hint 2: Look for algebraic properties, symmetry, or geometric theorems to simplify. (a – 3b)2 + (pb – 3c)2 = 0.

Hint 3: Proceed with the final algebraic steps to solve the system. a solve for the final valueb pb solve for the final valuec.

Solution

Step 1: a2 + 9b2 – 6ab + p2b2 – 6pbc + 9c2 = 0

Step 2: (a – 3b)2 + (pb – 3c)2 = 0

Step 3: a = 3b pb = 3c

Step 4: If is the largest side

Step 5: b+  3b

Step 6: p>6 …(i)

Step 7: If is largest side

Step 8: p < 12 …(ii)

Step 9: so, = {7, 8, 9, 10, 11}

Step 10: => Number of positive integral value of is 5

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    2024 IOQM 2024 Q10 - Olympiad Math Olympiad Question | Leminno