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8(abcd+1)>(a+1)(b+1)(c+1)(d+1) prove it

if a,b,c,d,all are greater than 1

Note by Aditya Kumar
4 years, 5 months ago

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What have you tried? What do you know?

As a hint : If \(x, y >1 \), then \( (x-1)(y-1) > 0 \) so \( xy + 1 > x + y \). Use this many times.

Calvin Lin Staff - 4 years, 5 months ago

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Just expand it , and try to put in square form , its very simple

Shivang Jindal - 4 years, 5 months ago

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I agree with just expand it. I'm not so sure what you mean by square form, though there is a way to write it as the sum of several positive (non-negative) terms.

Calvin Lin Staff - 4 years, 5 months ago

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I think, its from Challenge and thrill . right?

Shivang Jindal - 4 years, 5 months ago

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this question was from the beginning section of the book in inequalities so it does not require any prerequisities so i tried so solve this without am gm inequalitiy or any other but cannot solve it

Aditya Kumar - 4 years, 5 months ago

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As a hint : If \(x,y>1\), then \((x−1)(y−1)>0\) so \(xy+1>x+y\).

This looks very similar to the inequality, especially on the LHS. Use this many times.

Calvin Lin Staff - 4 years, 5 months ago

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Can someone explain it once more??...

Tanmay Dokania - 2 months, 2 weeks ago

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thanks i have now solved it

Aditya Kumar - 4 years, 5 months ago

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Try to substitute \(x=a-1, y=b-1, z=c-1, w=d-1\).

Shourya Pandey - 4 years, 5 months ago

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Don't you mean \(x=a+1,y=b+1\), etcetera?

Tim Vermeulen - 4 years, 5 months ago

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Try doing it, it becomes very easy

Shourya Pandey - 4 years, 5 months ago

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No

Shourya Pandey - 4 years, 5 months ago

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