Question

X + Y = 1 e X - Y = 3​

Answer 1

{X + Y = 1 ===> y=1-x

{X - Y = 3

--------------- (+)

2x. = 4

x = 2 ✓ =====> y=1-x = 1-2= -1 ✓

Answer 2

x+y=1. x=1-y. _. _

x-y=3 x-y=3. 1-y-y=3. -2y=3-1

_ _. x=1-(-1). x=2

y=2/-2. y=-1. y=-1. y=-1