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Let a and b be real numbers such that a^3+3ab^2=679 and 3a^2*b+b^3=-679. Find a+b.

 Oct 17, 2022
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Hi Guest!

If we added both equations we get:

a^3+3ab^2+3a^2b+b^3=0

Notice this is the expansion of a cubic.

Thus, (a+b)^3 = 0 

So this means, a+b=0

I hope this helps :).

 Oct 18, 2022

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