Find all pairs of real numbers satisfying the following conditions:
Solutions — 2
Solution 1
Answer: , .
Firstly, we obtain that
and hence we get
Let , , . Then we have
This shows that and it can be expressed as
The last equality implies that either or .
For , we obtain the solution .
Let . In this case using , we get . Consider the condition . Define , . In this case, we get
These two conditions imply that
By AM-GM, we get which is equivalent to or . From (*), we conclude that and hence . In this case since and we get that
Therefore, (*) holds only if and which implies that . This yields the solution . Both obtained solutions satisfy the problem conditions.
Solution 2
Let , . Then by AM-GM, we have and hence
Therefore, we get
Using (1), (2) and (3), we obtain the following solutions:
Hence, the only solutions are and . In both cases, and it follows that . The obtained solutions , satisfy the problem conditions.