1979 IMO Problems/Problem 5
Problem
Determine all real numbers a for which there exists positive reals which satisfy the relations
Solution
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See Also
1979 IMO (Problems) • Resources | ||
Preceded by Problem 4 |
1 • 2 • 3 • 4 • 5 • 6 | Followed by Problem 6 |
All IMO Problems and Solutions |
Let ,
and
. For all pairs
, let
Then we have on one hand
Therefore \\(1)
and on the other hand \\
(2)
Then from (1) we have
and from (2)
so
Besides we also have from (1)
and from (2)
and for
where in the right hand we have that
, so
,
and
, so
for
From the latter and (2) we also have
So we have that
If ,
take
,
for
. Then
,
, and