This is too Difficult for Me!

x 2 + 3 x + 3 3 + 2 x 2 + 3 x + 2 3 = 6 x 2 + 12 x + 8 \large \sqrt[3]{x^2+3x+3} + \sqrt[3]{2x^2+3x+2} = 6x^2 + 12x+8

What is the sum of all values of x x such that the above equation is satisfied.


The answer is -1.

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1 solution

Thanh Viet
Dec 18, 2014

So 1 \boxed{-1} is the answer.

Can you explain the steps please

Kudou Shinichi - 6 years, 5 months ago

It is not too clear to me how you applied CS. Can you add more details?

I believe that the inequalities are more clearly explained by saying that you applied AM-GM on ( x 2 + 3 x + 3 ) , 1 , 1 (x^2 + 3x + 3), 1, 1 and ( 2 x 2 + 3 x + 2 ) , 1 , 1 (2x^2 + 3x + 2), 1, 1 (and we can easily check that the quadratics are always positive).

This is an interesting approach, I wonder if there is a shorter approach.

Calvin Lin Staff - 6 years, 5 months ago

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Yes. As you said, I applied on ( x 2 + 3 x + 3 ) , 1 , 1 (x^2+3x+3), 1, 1 and ( 2 x 2 + 3 x + 2 ) , 1 , 1 (2x^2+3x+2), 1, 1 . Actually, this is a problem in a magazine. I will post the better solution from this magazine when it is available.

Thanh Viet - 6 years, 5 months ago

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