решите систему: x+y=4 3х -2у=17

Question

решите систему:

x+y=4

3х -2у=17

Answer 1

х=4-y

3(4-y)-2y=17

12-3y-2y=17

-5y=17-12

-5y=5

y=-1

x=4-(-1)=5

Answer 2

x + y = 4             x = 4 - y                         y = -1                 y = -1

3x - 2y = 17       3 (4-y) - 2y = 17           x = 4 - (-1)         x = 5

 

3(4 - y) - 2y = 17

12 - 3y - 2y = 17

- 5y = 17 - 12

- 5y = 5

y = -1

 

(5; -1)