Question

{21x+y=-15,1 {y=0,9-x

Answer 1

21x+0,9-x =-15,1
20x=-15,1-0.9
20x=-16
x=-16/20=-0.8
y=0.9-(-0.8)
y= 1,7
Ответ : x=-0.8 , y =1,7
( -0,8 ; 1,7)

Answer 2

Подставляем у = 0.9-x
21x + 0.9-x = -15.1
21x-x = -15.1-0.9
20x = -16
x = -16/20
x = -0.8

y = 0.9-(-0.8) = 0.9+0.8 = 1.7

Ответ: x = -0.8, y = 1.7