Question

Помогите пожалуйста решить
$\left \{ {{x+2y=3} \atop {3 x^{x+y}=81 }} \right.$

Answer 1

$\left \{ {{x+2y=3} \atop {3^{x-y} =81}} \right.$

$\left \{ {{x=3-2y} \atop {3^{x-y} =81}} \right.$

$\left \{ {{x=3-2y} \atop {3^{3-2y-y} =81}} \right.$

$\left \{ {{x=3-2y} \atop {3^{3-3y}=3^{4}}} \right.$

$3-3y=4$

$-3y=4-3$

$y=- \frac{1}{3}$

$x=3-2y=3- \frac{2}{3}=\frac{7}{3}=2\frac{1}{3}$