Question

Determine o valor do X e Y o sistema:

X + Y= 4 X- Y= 12


a) x= -4 é y= 8


b) x= 8 e y= 4


c) x=8 e y= -4


d) x= -8 e y= -​

Answer 1

$\large\boxed{\begin{array}{l}+\underline{\begin{cases}\sf x+\diagup\!\!\!\!y=4\\\sf x-\diagup\!\!\!\!y=12\end{cases}}\\\sf 2x=16\\\sf x=\dfrac{16}{2}\\\\\sf x=8\\\sf x+y=4\\\sf 8+y=4\\\sf y=4-8\\\sf y=-4\\\sf S=\{8,-4\}\\\huge\boxed{\boxed{\boxed{\boxed{\sf\red{\maltese}~\blue{alternativa~c}}}}}\end{array}}$