Week 64 Problem: Solve for x and y with Real Solutions Only

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The forum discussion centers on solving the equations $xy(x+y)=30$ and $x^3+y^3=35$ for real solutions of $x$ and $y$. The correct solutions were provided by members including MarkFL, BAdhi, kaliprasad, soroban, anemone, and Sudharaka. BAdhi's solution was highlighted as particularly effective in addressing the problem. The discussion emphasizes the importance of algebraic manipulation and understanding of polynomial identities in finding real solutions.

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Solve the following for $x$ and $y$ (real solutions only):

$xy(x+y)=30\\
x^3+y^3=35$
--------------------
 
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Congratulations to the following members for their correct solutions:

1) MarkFL
2) BAdhi
3) kaliprasad
4) soroban
5) anemone
6) Sudharaka

Solution (from BAdhi):
$\begin{align}
xy(x+y)&=30\qquad(1)\\
x^3+y^3&=35\qquad(2)\\
3(1)+(2)\implies \qquad x^3+3x^2y+3xy^2+y^3&=90+35\\
(x+y)^3&=125\\
(x+y)&=5\qquad (a)\\
\text{from (1)} \implies \qquad xy&=6\qquad (b)\\
\text{from (a)} \implies \qquad x(5-x)&=6\\
x^2-5x+6&=0\\
(x-2)(x-3)&=0\\
x=2,& x=3
\newline
\text{from (b)} \implies \qquad y=3,& y=2
\end{align}$

Therefore final answer is,
$$\text{$x=2$ and $y=3$}\\
\text{or}\\
\text{$x=3$ and $y=2$}$$
 

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