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National and Regional Contests
Russia Contests
Saint Petersburg Mathematical Olympiad
2023 Saint Petersburg Mathematical Olympiad
1
2-variable inequality
2-variable inequality
Source: St. Petersburg 2023 9.1
August 12, 2023
inequalities
Problem Statement
Let
a
,
b
>
1
a, b>1
a
,
b
>
1
be reals such that
a
+
1
a
2
≥
5
b
−
3
b
2
a+\frac{1}{a^2} \geq 5b-\frac{3}{b^2}
a
+
a
2
1
≥
5
b
−
b
2
3
. Show that
a
>
5
b
−
4
b
2
a>5b-\frac{4}{b^2}
a
>
5
b
−
b
2
4
.
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