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MathNet 2017-part-03 — 176 problems (EN–VI) Question 16

Math Olympiad Vault · MathNet 2017-part-03 — 176 problems (EN–VI)

Question 16

Let $a_{1}, a_{2}, \ldots, a_{n}, k$ and $M$ be positive integers with the properties
$$
\frac{1}{a_{1}}+\frac{1}{a_{2}}+\ldots+\frac{1}{a_{n}}=k \quad \text{ and } \quad a_{1} a_{2} \ldots a_{n}=M .
$$
Prove: if $M\gt 1$, the polynomial
$$
P(x)=M(x+1)^{k}-\left(x+a_{1}\right)\left(x+a_{2}\right) \ldots\left(x+a_{n}\right)
$$
has no positive roots.