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Spring Mathematical Tournament

Bulgaria algebra

Problem

Find all values of the real parameter such that the inequality holds true for every .
Solution
We have that , and . Then the inequality is equivalent to giving . Since and when we obtain:

1. For the inequality holds true iff .

2. For the inequality holds true iff and .

Therefore the desired values are .
Final answer
(1, 2)

Techniques

Logarithmic functionsExponential functions