Is this possible to find solutions?

Algebra Level 2

Real numbers a a , b b , and c c are such that a b c a \leq b \leq c and ( 1 + 1 a ) ( 1 + 1 b ) ( 1 + 1 c ) = 2 \left(1+\dfrac{1}{a}\right) \left(1+\dfrac{1}{b}\right) \left(1+\dfrac{1}{c}\right)=2

Are there any solutions satisfying these conditions?

Bonus: Prove the correct answer.

Paradoxical Answer. Yes No

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3 solutions

Chew-Seong Cheong
Dec 27, 2019

Let a = 2 a = -2 and b = c = 1 b=c=1 . Then a b c a \le b \le c and ( 1 1 2 ) ( 1 + 1 1 ) ( 1 + 1 1 ) = 2 \left(1-\dfrac 12\right)\left(1+\dfrac 11\right)\left(1+\dfrac 11\right) = 2 .

It is easy to check the a = b = c a=b=c case. In this case, the given equation becomes ( 1 + 1 a ) 3 = 2 (1+\dfrac{1}{a})^3=2 , or, as a real solution, 1 + 1 a = 2 3 1+\dfrac{1}{a}=\sqrt [3] {2} , or a = b = c = 1 2 3 1 a=b=c=\dfrac{1}{\sqrt [3] {2}-1} . Hence the answer is yes

Chris Lewis
Dec 26, 2019

Perhaps I'm missing something but a = b = c = 1 3 2 1 a=b=c=\frac{1}{^3{\sqrt2}-1} seems to work, so the answer is yes .

Unsolicited LaTeX \LaTeX advice:

You can type the radical like this:

\sqrt[3]{2}

Instead of

^3 \sqrt{2}

Take care!

Pi Han Goh - 1 year, 5 months ago

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