Multiple choice

If $\alpha$ and $\beta$ are the roots of the equation $x^{2} - 8x + p = 0$ such that $\alpha^{2} + \beta^{2} = 40$, find the value of $p$.

  1. $8$
  2. $10$
  3. $12$
  4. $14$
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C Correct answer
Explanation

alpha + beta = 8, alpha * beta = p. alpha^2 + beta^2 = (alpha + beta)^2 - 2*alpha*beta = 40. 8^2 - 2p = 40. 64 - 2p = 40. 2p = 24. p = 12.

AI explanation

Using Vieta's formulas for the equation x^2 - 8x + p = 0, the sum of the roots is a + b = 8, and the product is ab = p. The identity for the sum of squares states that a^2 + b^2 = (a + b)^2 - 2ab. Substituting the known values gives 40 = 8^2 - 2p. Solving this equation yields 40 = 64 - 2p, so 2p = 24, and p = 12.