Can you solve this inequality without using AM-GM?

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    Algebra Inequalities
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The discussion focuses on solving the inequality (pq + xy)(px + qy) ≥ 4pqxy without employing the AM-GM inequality. Participants demonstrate that by expanding the left-hand side and simplifying, the problem reduces to proving that for any positive integers x and y, the expression x/y + y/x ≥ 2 holds true. This conclusion is established through the quadratic inequality x² - 2x + 1 ≥ 0, which confirms the result for x > 0.

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lakshya91
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I have no idea how to solve this inequality without using AM-GM inequality:


for any positive integers p,q,x,y show that
(pq+xy)(px+qy)>=4pqxy
 
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Multiply out the brackets on the left hand side, and then divide everything by pqxy.

You are left with: p/y + y/p + q/x + x/q on the left. All there is left to do to prove the result is to show that for any positive integers x and y: x/y + y/x >= 2.
 
In general for x > 0, x + 1/x ≥ 2.
This is trivially proven by x2 -2x + 1 = (x-1)2 ≥ 0.
 

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