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jmc

algebra senior

Problem

Let and be the distinct roots of the equation Find
Solution
Consider the polynomial Note that is a polynomial of degree at most 4. Also, and This might lead us to conclude that but as we just observed, is a polynomial of degree 4.

So, consider the polynomial The polynomial becomes 0 at and Therefore, for some polynomial

Since is a polynomial of degree at most 4, is a polynomial of degree 5. Furthermore, the leading coefficient is 1. Therefore, and Then which expands as This is important, because the expression given in the problem is the coefficient of in Hence, the expression given in the problem is equal to By Vieta's formulas, this is
Final answer
-7