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Printjmc
algebra intermediate
Problem
Find the sum of all complex roots of the equation given that there are no repeated roots.
Solution
We seek to use Vieta's formulas. To be able to apply the formulas, we multiply both sides by to eliminate the fractions. This gives (Be careful! We may have introduced one of the roots into this equation when we multiplied by However, note that none of satisfy our new equation, since plugging each one in gives the false equation Therefore, the roots of this new polynomial equation are the same as the roots of the original equation, and we may proceed.)
The left-hand side has degree while the right-hand side has degree so when we move all the terms to the right-hand side, we will have a th degree polynomial equation. To find the sum of the roots, it suffices to know the coefficients of and
The coefficient of on the right-hand side is while the coefficients of on the left-hand and right-hand sides are and respectively. Therefore, when we move all the terms to the right-hand side, the resulting equation will be of the form It follows that the sum of the roots is
The left-hand side has degree while the right-hand side has degree so when we move all the terms to the right-hand side, we will have a th degree polynomial equation. To find the sum of the roots, it suffices to know the coefficients of and
The coefficient of on the right-hand side is while the coefficients of on the left-hand and right-hand sides are and respectively. Therefore, when we move all the terms to the right-hand side, the resulting equation will be of the form It follows that the sum of the roots is
Final answer
43