Question

Решите систему уравнений 7x+2y=-5 3x-y=9

Answer 1

hi

7x+2y = -5

3x-y = 9

first thing is to define one letter by it's value in the second.

here we have 3x-y = 9 so

-y = 9 -3x

y = 3x-9

then with y = 3x-9 ,

7x +2y = -5 ⇔ 7x + 2 ( 3x-9) = -5

so :

7x + 2 ( 3x-9) = -5

7x +6x -18 = -5

13x -18 = -5

13x = -5 +18

13x = 13

x = 13/13

x = 1

as : y = 3x-9 so bhy remplacing X by it's value

y = 3 (1) - 9 = 3-9 = -6

y = -6

solutions are :

x = 1 and y = -6

let' s check to be sure :

7 (1) + 2 (-6) = 7 -12 = -5

and 3(1) - (-6) = 3 +6 = 9