Question

Resuelve los siguientes sistemas de ecuaciones lineales de dos por dos
de dos ​

Answer 1

1) 2x - 5y = 20 // 2x + 5y = 10

4x = 30

x = 30/4

x = 15/2

2(15/2) -5y = 20

15 -5y = 20

5y = -5

y = -1

2) 6x - 5y = 28 // 4x + 9y = -6

6x = 28 + 5y

x = 28 + 5y/6

4.(28 + 5y/6) + 9y = -6

112 + 20y/6 + 9y = -6

112 + 20y + 54y = -36

74y = - 148

y = -148/74

y = -2

4x + 9.(-2) = -6

4x - 18 = -6

4x = 12

x = 3

3) 8x + y = 21 // 3x + y = 11

5x = 10

x = 2

3.2 + y = 11

y = 5