Respostas

2014-08-17T20:23:46-03:00
Oi,

multiplique a equação I por -2 e some com a equação II:

+\begin{cases}-4x-12y=-20~~(I)\\
~~4x-2y=-1~~(II) \end{cases}\\
~~~~------\\
~~~~~~~~~~~-14y~~=~~-21\\\\
~~~~~~~~~~~~y= \dfrac{-21}{-14}\\\\
~~~~~~~~~~~~~~~y= \dfrac{7}{2}\\\\\\
4x-2y=-1\\\\
4x-2\cdot \dfrac{7}{2}=-1\\\\
4x-7=-1\\
4x=-1+7\\
4x=6\\\\
x= \dfrac{6}{4}= \dfrac{3}{2}\\\\\\
\large\boxed{\boxed{S=\left\{\left( \dfrac{3}{2},~ \dfrac{7}{2}\right)\right\}}}

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