Question

Как найти Y? и обьесните ​

Answer 1

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$\displaystyle \bf \left \{ {{x+y=5} \atop {x-y=8}} \right. \:\ \left \{ {{x=5-y} \atop {5-y-y=8}} \right. \:\ \left \{ {{x=6.5} \atop {y=1.5}} \right.$

$\displasystyle \bf 5-y-y=8\\\\5-2y=8\\\\-2y=8-5\\\\-2y=3\\\\y=\frac{3}{-2} \\\\y=-1.5$

$\: \boxed{\displasystyle \bf \Big \: y=-1.5}$

Answer 2

$\displaystyle\bf\\\left \{ {{x+y=5} \atop {x-y=8} \ |\cdot(-1)} \right. \\\\\\+\left \{ {{x+y=5} \atop {-x+y=-8}} \right. \\--------\\\\2y=-3\\\\\boxed{y=-1,5}$