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2010 Math Kangaroo

Problem 9

Problem 9 · 2010 Math Kangaroo Medium
Algebra & Patterns sum-constraint

How many two-digit numbers with x in the tens column and y in the units column have the property (x−3)² + (y−2)² = 0?

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Answer: A — 1
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Hint 1 of 2
A sum of two squares equals zero only one way.
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Hint 2 of 2
Each square must be zero on its own.
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Approach: sum of squares is zero only when each term is zero
  1. (x−3)² + (y−2)² = 0 forces both squares to be 0.
  2. So x = 3 and y = 2, giving the single number 32.
  3. Exactly 1 two-digit number works.
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