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jmc

algebra intermediate

Problem

Find the sum of all real numbers such that .
Solution
Because the problem only asks about the real roots of the polynomial, we can't apply Vieta's formulas directly. Instead, we recognize the coefficients from the expansion of : Seeing this, we subtract from both sides, giving Hence, Let Then so This expands to Consider the function Then and is increasing on so there is exactly one positive value of for which Also, if then

This means that there are exactly two solutions in and if is one solution, then the other solution is Therefore, the sum of the solutions is
Final answer
1