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Difficulty: 3/102022 IOQM 2022 (Q5)

Let be the smallest positive integer such that m2 + (m + 1)2 + … + (m + 10)2 is the square of positive integer n. Find + n.

Guide / Hint

Hint 1: Start by analyzing the initial conditions and setting up the basic equations.  (m   1)2  11m 2  (12  22  32  \dots  102 )  2m(1  2  3  \dots  10).

Hint 2: Look for algebraic properties, symmetry, or geometric theorems to simplify. = 11(m2 + 10m + 35).

Hint 3: Proceed with the final algebraic steps to solve the system. solve for the final value((m + 5)2 + 10).

Solution

Step 1:  (m   1)2  11m 2  (12  22  32  \dots  102 )  2m(1  2  3  \dots  10)

Step 2: = 11(m2 + 10m + 35)

Step 3: = 11((m + 5)2 + 10)

Step 4: The least possible value of = 18

Step 5: The required sum = 11(232 + 10)

Step 6: = 11 × 11 × 49

Step 7: Then, = 18 and = 77

Step 8: => + = 95

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    2022 IOQM 2022 Q5 - Olympiad Math Olympiad Question | Leminno