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Old 2004-04-27, 12:06   #12
jinydu
 
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Dec 2003
Hopefully Near M48

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Quote:
Originally Posted by Bob Silverman
a^3 + b^3 = 20
ab = -2
x = 2
x^3 = (a+b)^3 = 8
I'm not sure what else you are looking for.
The problem is with the third line (x = 2). I wanted to simplify cbr(10 + sqrt(108)) + cbr(10 - sqrt(108)) without knowing a priori that the answer is 2.

That way, it would be possible to generalize the technique to cases where I don't know what x equals to beforehand.
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