What Is the Maximum Value of \(a^2+ab+2b^2\) Given \(a^2-ab+2b^2=8\)?

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The maximum value of the expression \(a^2 + ab + 2b^2\) given the constraint \(a^2 - ab + 2b^2 = 8\) is determined through optimization techniques. By substituting \(b\) in terms of \(a\) and applying methods such as Lagrange multipliers or completing the square, the maximum value can be calculated. The discussion emphasizes the importance of showing the solution process to validate the approach used in arriving at the final answer.

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$a$ and $b$ are positive real numbers such that $a^2-ab+2b^2=8$.

Find the maximum value of $a^2+ab+2b^2$.
 
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Here:

$\frac{4}{7}(4+\sqrt2)^2$
 
conscipost said:
Here:

$\frac{4}{7}(4+\sqrt2)^2$

Your answer is correct, conscipost! (Yes) Well done!

But I'd appreciate it if you show your solution (but not merely the final answer) so we know what approach you used, sounds good to you?
 

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