Two numbers have sum 24 and product 143. Compute the sum of their squares.

Difficulty: Easy

Correct Answer: 290

Explanation:


Introduction / Context:
This is a classic identity application: from sum and product of two numbers, determine the sum of their squares quickly.


Given Data / Assumptions:

  • Let the numbers be a and b.
  • a + b = 24; ab = 143.


Concept / Approach:
Use the identity a^2 + b^2 = (a + b)^2 − 2ab. This avoids solving for a and b explicitly.


Step-by-Step Solution:

(a + b)^2 = 24^2 = 5762ab = 2 * 143 = 286a^2 + b^2 = 576 − 286 = 290


Verification / Alternative check:
Solving: the numbers are 11 and 13 (since t^2 − 24t + 143 = 0 → roots 11, 13). Then 11^2 + 13^2 = 121 + 169 = 290, confirming the identity method.


Why Other Options Are Wrong:
296, 295, and 228 do not match the identity result; they typically come from arithmetic slips (e.g., subtracting ab instead of 2ab).


Common Pitfalls:
Forgetting the factor 2 in 2ab; attempting a longer route by solving for the numbers when the identity is faster and safer.


Final Answer:
290

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