Răspuns:
2.
1-4x+y = 0
y = 4x -1
-2x + 3y = 10
-2x + 3(4x-1) = 10
-2x + 12x - 3 = 10
10x = 13
x = 1.3
y = 4x - 1 = 4 × 1.3 -1
y = 4.2
3.
a) 2x + 4y = 6
2x = 6 - 4y
x = 3 - 2y
6x + 3y = 5
6(3-2y) + 3y = 5
18 - 12y + 3y = 5
-9y = -13
y = 13/9
x = 3 - 2y = 3 - 2 × 13/9
x = 1/9
b) 8a - 4b = -4
4b = 8a +4
b = 2a + 1
2a + 5b = 2
2a + 5(2a + 1) = 2
2a + 10a + 5 = 2
12a = -3
a = -1/4
a = -0.25
b = 2a + 1
b = 2 × (-1/4) + 1
b = 1/2
b = 0.5