Problems

Age
Difficulty
Found: 5

The quadratic trinomials \(f (x)\) and \(g (x)\) are such that \(f' (x) g' (x) \geq | f (x) | + | g (x) |\) for all real \(x\). Prove that the product \(f (x) g (x)\) is equal to the square of some trinomial.

Prove that the following polynomial does not have any identical roots: \(P(x) = 1 + x + x^2/2! + \dots + x^n/n!\)

Prove that the polynomial \(x^{2n} - nx^{n + 1} + nx^{n - 1} - 1\) for \(n > 1\) has a triple root of \(x = 1\).

Prove that the polynomial \(P (x) = a_0 + a_1x + \dots + a_nx^n\) has a number \(-1\) which is a root of multiplicity \(m + 1\) if and only if the following conditions are satisfied: \[\begin{aligned} a_0 - a_1 + a_2 - a_3 + \dots + (-1)^{n}a_n &= 0,\\ - a_1 + 2a_2 - 3a_3 + \dots + (-1)^{n}na_n &= 0,\\ \dots \\ - a_1 + 2^{m}a_2 - 3^{m}a_3 + \dots + (-1)^{n}n^{m}a_n &= 0. \end{aligned}\]

Hercules meets the three-headed snake Hydra of Lerna. Every minute, Hercules chops off one head of the snake. Let \(x\) be the survivability of the snake (\(x > 0\)). The probability \(p_s\) of the fact that in the place of the severed head will grow s new heads \((s = 0, 1, 2)\) is equal to \(\frac{x^s}{1 + x + x^2}\).

During the first 10 minutes of the battle, Hercules recorded how many heads grew in place of each chopped off one. The following vector was obtained: \(K = (1, 2, 2, 1, 0, 2, 1, 0, 1, 2)\). Find the value of the survivability of the snake, under which the probability of the vector \(K\) is greatest.