Question

решите систему уравнений {x+y=1 {x^2-y^2=9

Answer 1

x = 1 - y
(1 - y)^2 - y^2 = 9*

1 - 2y + y^2 - y^2 - 9 = 0
- 2y - 8 = 0 
- 2y = 8
2y = - 8
y = - 4

x = 1 + 4 = 5
y = - 4 

Ответ
( 5; - 4)