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Question

If r and s are the roots of x^2-px+q=0, then r^2+s^2 equals:

Accepted Answer

We can write r^2+s^2 in terms of the sum of the roots (r+s) and the products of the roots (rs): r^2 + s^2 = (r+s)^2 - 2rs = p^2 - 2q The answer is p^2-2q.