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Winter Mathematical Competition

Bulgaria algebra

Problem

The functions and are given. Find all real values of such that:

a) is a positive integer;

b) the inequality holds.
Solution
a) Hint. Set , where is a positive integer. Then and use the fact that the discriminant of this quadratic equation is nonnegative.

Answer. .

b) Answer. .
Final answer
a) x = (-3 + sqrt(33)) / 2, (-3 - sqrt(33)) / 2, 2. b) x ∈ (-∞, -2] ∪ [1, ∞).

Techniques

Quadratic functionsLinear and quadratic inequalities