Răspuns:
1. S (1,2)
2. S (1,1)
3. S (7/2,4)
Explicație pas cu pas:
1.
(x+2y=5
(x-y= -1
(x= 5-2y
(x-y= -1
(x=5-2y
(5-2y-y= -1
(x=5-2y
(5-3y= -1
(x=5-2y
(-3y= -1-5
(x=5-2y
(-3y=-6/:(-3)
(x=5-2y
(y=2
(x=5-4
(y=2
(x=1
(y=2
2.
(2x -y = 1
(x +3y =4
(2x = 1 + y
(x +3y=4
(x= 1 + y supra 2
(1 + y/2 +3y=4
(x= 1 +y/2
(1 + y +6y=8
(x=1+y/2
(7y= 7/:7
(x=1+y/2
(y=1
(x=1
(y=1
3.
(2x +3y =19
(4x+11y =53
(2x = 19 -3y
(4x+11y=53
(x= 19 -3y/2
(4x+11y=53
(x=19-3y/2
(19-3y/2+11y=53
(x=19-3y/2
(19-3y+22y=106
(x=19-3y/2
(19y=87
(x=19-3y/2
(y=4
(x=19-12/2
(y=4
(x=7/2
(y=4