Question

решите на множестве действительных чисел систему уравнений (3x+y=-1
(x-y=5​

Answer 1

Răspuns:

Substitutie :

3x + y = -1 => y = -1 - 3x

x - y = 5

x - (- 1 - 3x) = 5

x + 1 + 3x = 5

4x = 5 - 1

4x = 4

x = 1

y = -1 - 3

y = -4

Reducere:

3x + y = -1

x - y = 5 (×3)

3x + y = -1

3x - 3y = 15

4y = -16

y = -4

x + 4 = 5

x = 5 - 4

x = 1