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May 5th, 2018, 08:07 AM   #1
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From: Bucharest

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Need some help with this..I don't know what to do at b)

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May 5th, 2018, 08:22 AM   #2
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at worst you can just evaluate the determinant.

$d = a(a^2-bc) - b(ac -b^2) + c(c^2-ab)$

then a bit of algebra will get you to the result they want. I leave that to you.
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May 5th, 2018, 08:32 AM   #3
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If you've done part (a), you know how to evaluate a 3×3 determinant.

Hence you should understand why d = a³ + b³ + c³ - 3abc.

The right-hand side factorizes as (a + b + c)(a² + b² + c² - ab - ac - bc),
which can easily be shown to be equivalent to the expression for d given in part (b).
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