Question

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Answer 1

b) $\left \{ {{x + y-2} \atop {4x-2y=5}}$ multi a 1° equac. por 2
$\left \{ {{2x+2y=2} \atop {4x-2y=5}} \right.$ 
2x=7
x= $\frac{7}{2}$
$2x + 2y= 2 \\\\ 2* \frac{7}{2} + 2y=2 \\\\ \frac{14}{2} +2y = 2 \\\\ 7+2y=2 \\\\ 2y=2-7 \\ y= \frac{-5}{2} = \\ y= -2,5$
$4x + 2y = 5 \\ 4x - 2*2,5= 5 \\ 4x-5=5 \\ 4x= 5+5 \\ x= \frac{10}{4} \\\\ x= \frac{5}{2} \\ x=2,5$

$4x+2y=5 \\ 4*(2,5) + 2 * (-2,5) = 5 \\ 10 - 5 = 5$

c) $\left \{ {{2x+3y=1} \atop {2x+5y=-1}} \right.$ multiplica a 2° eq. por (-1)
$\left \{ {{2x+3y=1} \atop {-2x-5y=1}} \right.$
-2y = 2           multip (-1)
$2y=-2 \\ y= \frac{-2}{2} \\ <strong>y= -1</strong>$

$2x+3y=1 \\ 2x+3*(-1)=1 \\ 2x -3 = 1 \\ 2x= 1+3 \\ x= \frac{4}{2} \\ x=2$

$2x+3y=1 \\ 2*2 + 3*(-1) = 1 \\ 4-3=1$