Question

Система
x+y=4
x-y=8

Нужно найти x и y.

Answer 1

{x+y=4      {x=4-y
{x-y=8       {(4-y)-y=8

4-y-y=8
-2y=4
y=4:(-2)
y=-2

x=4-(-2)
x=6
Ответ: (6;-2)

Answer 2

x+y=4
x=4-y
x-y=8
4-y-y=8
4-2y=8
2y=4-8
2y=-4
y=-2
x=4-(-2)
x=6
(6;-2)