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Given that $a+b=5$ and $a^2+b^2=15$ , find $a^3+b^3$ .

Havingfun May 19, 2019

2⁺⁰ Answers

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$a^3 + b^3 = (a+b)(a^2 -ab +b^2)=\\ (a+b)^2 = a^2 + b^2 + 2ab=15+2ab=25\\ 2ab=10\\ ab=5\\ a^3+b^3=5(15-5)=50$

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Rom May 19, 2019

edited by Rom May 19, 2019

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That was much simpler than what I was thinking

Havingfun May 25, 2019

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