Question

5. No sistema, x + y = 4 podemos afirmar que:
. .x - 3y = - 4
a) x = y
b) x = 0 e y = 4
c) x>y
d) x = 4e y = 0

urgente!!!!!!​​

Answer 1

$\Large\boxed{\begin{array}{l}\begin{cases}\sf x+y=4\\\sf x-3y=-4\end{cases}\\+\underline{\begin{cases}\sf 3x+\diagdown\!\!\!\!\!\!3y=12\\\sf x-\diagdown\!\!\!\!\!\!3y=-4\end{cases}}\\\sf 4x=8\\\sf x=\dfrac{8}{4}\\\\\sf x=2\\\sf x+y=4\\\sf 2+y=4\\\sf y=4-2\\\sf y=2\\\huge\boxed{\boxed{\boxed{\boxed{\sf\maltese~alternativa~a}}}} \end{array}}$