Find two positive numbers whose sum is 15 and the sum of whose squares is minimum. The numbers are:

Find two positive numbers whose sum is 15 and the sum of whose squares is minimum. The numbers are:

• A. 7.5 and 7.5
• B. 10 and 5
• C. 8 and 7
• D. 9 and 6

Answer: A) 7.5 and 7.5

Explanation: Let numbers be x and 15-x. Sum of squares S = x² + (15-x)². S' = 2x - 2(15-x) = 4x - 30. S' = 0 gives x = 7.5. The numbers are 7.5 and 7.5.