Numerical: quadratic equations MCQ - Practice Questions with Answers

For the quadratic equation x^2 + px + q = 0, the sum of the roots is m + n = -p and the product is mn = q. Now m^2 + n^2 = (m + n)^2 - 2mn. Substituting these values gives (-p)^2 - 2q, which simplifies to p^2 - 2q. Expressions with +2q, +q, or -q do not follow from subtracting twice the product of the roots, so they are not correct.